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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Internet Engineering Task Force E. Grossman, Ed. 3 Internet-Draft DOLBY 4 Intended status: Informational C. Gunther 5 Expires: January 5, 2017 HARMAN 6 P. Thubert 7 P. Wetterwald 8 CISCO 9 J. Raymond 10 HYDRO-QUEBEC 11 J. Korhonen 12 BROADCOM 13 Y. Kaneko 14 Toshiba 15 S. Das 16 Applied Communication Sciences 17 Y. Zha 18 HUAWEI 19 B. Varga 20 J. Farkas 21 Ericsson 22 F. Goetz 23 J. Schmitt 24 Siemens 25 July 4, 2016 27 Deterministic Networking Use Cases 28 draft-ietf-detnet-use-cases-10 30 Abstract 32 This draft documents requirements in several diverse industries to 33 establish multi-hop paths for characterized flows with deterministic 34 properties. In this context deterministic implies that streams can 35 be established which provide guaranteed bandwidth and latency which 36 can be established from either a Layer 2 or Layer 3 (IP) interface, 37 and which can co-exist on an IP network with best-effort traffic. 39 Additional requirements include optional redundant paths, very high 40 reliability paths, time synchronization, and clock distribution. 41 Industries considered include wireless for industrial applications, 42 professional audio, electrical utilities, building automation 43 systems, radio/mobile access networks, automotive, and gaming. 45 For each case, this document will identify the application, identify 46 representative solutions used today, and what new uses an IETF DetNet 47 solution may enable. 49 Status of This Memo 51 This Internet-Draft is submitted in full conformance with the 52 provisions of BCP 78 and BCP 79. 54 Internet-Drafts are working documents of the Internet Engineering 55 Task Force (IETF). Note that other groups may also distribute 56 working documents as Internet-Drafts. The list of current Internet- 57 Drafts is at http://datatracker.ietf.org/drafts/current/. 59 Internet-Drafts are draft documents valid for a maximum of six months 60 and may be updated, replaced, or obsoleted by other documents at any 61 time. It is inappropriate to use Internet-Drafts as reference 62 material or to cite them other than as "work in progress." 64 This Internet-Draft will expire on January 5, 2017. 66 Copyright Notice 68 Copyright (c) 2016 IETF Trust and the persons identified as the 69 document authors. All rights reserved. 71 This document is subject to BCP 78 and the IETF Trust's Legal 72 Provisions Relating to IETF Documents 73 (http://trustee.ietf.org/license-info) in effect on the date of 74 publication of this document. Please review these documents 75 carefully, as they describe your rights and restrictions with respect 76 to this document. Code Components extracted from this document must 77 include Simplified BSD License text as described in Section 4.e of 78 the Trust Legal Provisions and are provided without warranty as 79 described in the Simplified BSD License. 81 Table of Contents 83 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 5 84 2. Pro Audio and Video . . . . . . . . . . . . . . . . . . . . . 5 85 2.1. Use Case Description . . . . . . . . . . . . . . . . . . 5 86 2.1.1. Uninterrupted Stream Playback . . . . . . . . . . . . 6 87 2.1.2. Synchronized Stream Playback . . . . . . . . . . . . 6 88 2.1.3. Sound Reinforcement . . . . . . . . . . . . . . . . . 7 89 2.1.4. Deterministic Time to Establish Streaming . . . . . . 8 90 2.1.5. Secure Transmission . . . . . . . . . . . . . . . . . 8 91 2.1.5.1. Safety . . . . . . . . . . . . . . . . . . . . . 8 92 2.2. Pro Audio Today . . . . . . . . . . . . . . . . . . . . . 8 93 2.3. Pro Audio Future . . . . . . . . . . . . . . . . . . . . 9 94 2.3.1. Layer 3 Interconnecting Layer 2 Islands . . . . . . . 9 95 2.3.2. High Reliability Stream Paths . . . . . . . . . . . . 9 96 2.3.3. Integration of Reserved Streams into IT Networks . . 9 97 2.3.4. Use of Unused Reservations by Best-Effort Traffic . . 9 98 2.3.5. Traffic Segregation . . . . . . . . . . . . . . . . . 10 99 2.3.5.1. Packet Forwarding Rules, VLANs and Subnets . . . 10 100 2.3.5.2. Multicast Addressing (IPv4 and IPv6) . . . . . . 10 101 2.3.6. Latency Optimization by a Central Controller . . . . 11 102 2.3.7. Reduced Device Cost Due To Reduced Buffer Memory . . 11 103 2.4. Pro Audio Asks . . . . . . . . . . . . . . . . . . . . . 12 104 3. Electrical Utilities . . . . . . . . . . . . . . . . . . . . 12 105 3.1. Use Case Description . . . . . . . . . . . . . . . . . . 12 106 3.1.1. Transmission Use Cases . . . . . . . . . . . . . . . 12 107 3.1.1.1. Protection . . . . . . . . . . . . . . . . . . . 12 108 3.1.1.2. Intra-Substation Process Bus Communications . . . 18 109 3.1.1.3. Wide Area Monitoring and Control Systems . . . . 19 110 3.1.1.4. IEC 61850 WAN engineering guidelines requirement 111 classification . . . . . . . . . . . . . . . . . 20 112 3.1.2. Generation Use Case . . . . . . . . . . . . . . . . . 21 113 3.1.3. Distribution use case . . . . . . . . . . . . . . . . 22 114 3.1.3.1. Fault Location Isolation and Service Restoration 115 (FLISR) . . . . . . . . . . . . . . . . . . . . . 22 116 3.2. Electrical Utilities Today . . . . . . . . . . . . . . . 23 117 3.2.1. Security Current Practices and Limitations . . . . . 23 118 3.3. Electrical Utilities Future . . . . . . . . . . . . . . . 25 119 3.3.1. Migration to Packet-Switched Network . . . . . . . . 25 120 3.3.2. Telecommunications Trends . . . . . . . . . . . . . . 26 121 3.3.2.1. General Telecommunications Requirements . . . . . 26 122 3.3.2.2. Specific Network topologies of Smart Grid 123 Applications . . . . . . . . . . . . . . . . . . 27 124 3.3.2.3. Precision Time Protocol . . . . . . . . . . . . . 28 125 3.3.3. Security Trends in Utility Networks . . . . . . . . . 29 126 3.4. Electrical Utilities Asks . . . . . . . . . . . . . . . . 31 127 4. Building Automation Systems . . . . . . . . . . . . . . . . . 31 128 4.1. Use Case Description . . . . . . . . . . . . . . . . . . 31 129 4.2. Building Automation Systems Today . . . . . . . . . . . . 31 130 4.2.1. BAS Architecture . . . . . . . . . . . . . . . . . . 32 131 4.2.2. BAS Deployment Model . . . . . . . . . . . . . . . . 33 132 4.2.3. Use Cases for Field Networks . . . . . . . . . . . . 35 133 4.2.3.1. Environmental Monitoring . . . . . . . . . . . . 35 134 4.2.3.2. Fire Detection . . . . . . . . . . . . . . . . . 35 135 4.2.3.3. Feedback Control . . . . . . . . . . . . . . . . 36 136 4.2.4. Security Considerations . . . . . . . . . . . . . . . 36 137 4.3. BAS Future . . . . . . . . . . . . . . . . . . . . . . . 36 138 4.4. BAS Asks . . . . . . . . . . . . . . . . . . . . . . . . 37 139 5. Wireless for Industrial . . . . . . . . . . . . . . . . . . . 37 140 5.1. Use Case Description . . . . . . . . . . . . . . . . . . 37 141 5.1.1. Network Convergence using 6TiSCH . . . . . . . . . . 38 142 5.1.2. Common Protocol Development for 6TiSCH . . . . . . . 38 143 5.2. Wireless Industrial Today . . . . . . . . . . . . . . . . 39 144 5.3. Wireless Industrial Future . . . . . . . . . . . . . . . 39 145 5.3.1. Unified Wireless Network and Management . . . . . . . 39 146 5.3.1.1. PCE and 6TiSCH ARQ Retries . . . . . . . . . . . 41 147 5.3.2. Schedule Management by a PCE . . . . . . . . . . . . 42 148 5.3.2.1. PCE Commands and 6TiSCH CoAP Requests . . . . . . 42 149 5.3.2.2. 6TiSCH IP Interface . . . . . . . . . . . . . . . 43 150 5.3.3. 6TiSCH Security Considerations . . . . . . . . . . . 44 151 5.4. Wireless Industrial Asks . . . . . . . . . . . . . . . . 44 152 6. Cellular Radio . . . . . . . . . . . . . . . . . . . . . . . 44 153 6.1. Use Case Description . . . . . . . . . . . . . . . . . . 44 154 6.1.1. Network Architecture . . . . . . . . . . . . . . . . 44 155 6.1.2. Delay Constraints . . . . . . . . . . . . . . . . . . 45 156 6.1.3. Time Synchronization Constraints . . . . . . . . . . 46 157 6.1.4. Transport Loss Constraints . . . . . . . . . . . . . 48 158 6.1.5. Security Considerations . . . . . . . . . . . . . . . 48 159 6.2. Cellular Radio Networks Today . . . . . . . . . . . . . . 49 160 6.2.1. Fronthaul . . . . . . . . . . . . . . . . . . . . . . 49 161 6.2.2. Midhaul and Backhaul . . . . . . . . . . . . . . . . 49 162 6.3. Cellular Radio Networks Future . . . . . . . . . . . . . 50 163 6.4. Cellular Radio Networks Asks . . . . . . . . . . . . . . 52 164 7. Industrial M2M . . . . . . . . . . . . . . . . . . . . . . . 52 165 7.1. Use Case Description . . . . . . . . . . . . . . . . . . 52 166 7.2. Industrial M2M Communication Today . . . . . . . . . . . 53 167 7.2.1. Transport Parameters . . . . . . . . . . . . . . . . 54 168 7.2.2. Stream Creation and Destruction . . . . . . . . . . . 55 169 7.3. Industrial M2M Future . . . . . . . . . . . . . . . . . . 55 170 7.4. Industrial M2M Asks . . . . . . . . . . . . . . . . . . . 55 171 8. Use Case Common Elements . . . . . . . . . . . . . . . . . . 55 172 9. Use Cases Explicitly Out of Scope for DetNet . . . . . . . . 56 173 9.1. DetNet Scope Limitations . . . . . . . . . . . . . . . . 57 174 9.2. Internet-based Applications . . . . . . . . . . . . . . . 57 175 9.2.1. Use Case Description . . . . . . . . . . . . . . . . 57 176 9.2.1.1. Media Content Delivery . . . . . . . . . . . . . 58 177 9.2.1.2. Online Gaming . . . . . . . . . . . . . . . . . . 58 178 9.2.1.3. Virtual Reality . . . . . . . . . . . . . . . . . 58 179 9.2.2. Internet-Based Applications Today . . . . . . . . . . 58 180 9.2.3. Internet-Based Applications Future . . . . . . . . . 58 181 9.2.4. Internet-Based Applications Asks . . . . . . . . . . 58 182 9.3. Pro Audio and Video - Digital Rights Management (DRM) . . 59 183 9.4. Pro Audio and Video - Link Aggregation . . . . . . . . . 59 184 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 60 185 10.1. Pro Audio . . . . . . . . . . . . . . . . . . . . . . . 60 186 10.2. Utility Telecom . . . . . . . . . . . . . . . . . . . . 60 187 10.3. Building Automation Systems . . . . . . . . . . . . . . 60 188 10.4. Wireless for Industrial . . . . . . . . . . . . . . . . 60 189 10.5. Cellular Radio . . . . . . . . . . . . . . . . . . . . . 61 190 10.6. Industrial M2M . . . . . . . . . . . . . . . . . . . . . 61 191 10.7. Internet Applications and CoMP . . . . . . . . . . . . . 61 192 11. Informative References . . . . . . . . . . . . . . . . . . . 61 193 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 70 195 1. Introduction 197 This draft presents use cases from diverse industries which have in 198 common a need for deterministic streams, but which also differ 199 notably in their network topologies and specific desired behavior. 200 Together, they provide broad industry context for DetNet and a 201 yardstick against which proposed DetNet designs can be measured (to 202 what extent does a proposed design satisfy these various use cases?) 204 For DetNet, use cases explicitly do not define requirements; The 205 DetNet WG will consider the use cases, decide which elements are in 206 scope for DetNet, and the results will be incorporated into future 207 drafts. Similarly, the DetNet use case draft explicitly does not 208 suggest any specific design, architecture or protocols, which will be 209 topics of future drafts. 211 We present for each use case the answers to the following questions: 213 o What is the use case? 215 o How is it addressed today? 217 o How would you like it to be addressed in the future? 219 o What do you want the IETF to deliver? 221 The level of detail in each use case should be sufficient to express 222 the relevant elements of the use case, but not more. 224 At the end we consider the use cases collectively, and examine the 225 most significant goals they have in common. 227 2. Pro Audio and Video 229 2.1. Use Case Description 231 The professional audio and video industry ("ProAV") includes: 233 o Music and film content creation 235 o Broadcast 237 o Cinema 239 o Live sound 240 o Public address, media and emergency systems at large venues 241 (airports, stadiums, churches, theme parks). 243 These industries have already transitioned audio and video signals 244 from analog to digital. However, the digital interconnect systems 245 remain primarily point-to-point with a single (or small number of) 246 signals per link, interconnected with purpose-built hardware. 248 These industries are now transitioning to packet-based infrastructure 249 to reduce cost, increase routing flexibility, and integrate with 250 existing IT infrastructure. 252 Today ProAV applications have no way to establish deterministic 253 streams from a standards-based Layer 3 (IP) interface, which is a 254 fundamental limitation to the use cases described here. Today 255 deterministic streams can be created within standards-based layer 2 256 LANs (e.g. using IEEE 802.1 AVB) however these are not routable via 257 IP and thus are not effective for distribution over wider areas (for 258 example broadcast events that span wide geographical areas). 260 It would be highly desirable if such streams could be routed over the 261 open Internet, however solutions with more limited scope (e.g. 262 enterprise networks) would still provide a substantial improvement. 264 The following sections describe specific ProAV use cases. 266 2.1.1. Uninterrupted Stream Playback 268 Transmitting audio and video streams for live playback is unlike 269 common file transfer because uninterrupted stream playback in the 270 presence of network errors cannot be achieved by re-trying the 271 transmission; by the time the missing or corrupt packet has been 272 identified it is too late to execute a re-try operation. Buffering 273 can be used to provide enough delay to allow time for one or more 274 retries, however this is not an effective solution in applications 275 where large delays (latencies) are not acceptable (as discussed 276 below). 278 Streams with guaranteed bandwidth can eliminate congestion on the 279 network as a cause of transmission errors that would lead to playback 280 interruption. Use of redundant paths can further mitigate 281 transmission errors to provide greater stream reliability. 283 2.1.2. Synchronized Stream Playback 285 Latency in this context is the time between when a signal is 286 initially sent over a stream and when it is received. A common 287 example in ProAV is time-synchronizing audio and video when they take 288 separate paths through the playback system. In this case the latency 289 of both the audio and video streams must be bounded and consistent if 290 the sound is to remain matched to the movement in the video. A 291 common tolerance for audio/video sync is one NTSC video frame (about 292 33ms) and to maintain the audience perception of correct lip sync the 293 latency needs to be consistent within some reasonable tolerance, for 294 example 10%. 296 A common architecture for synchronizing multiple streams that have 297 different paths through the network (and thus potentially different 298 latencies) is to enable measurement of the latency of each path, and 299 have the data sinks (for example speakers) delay (buffer) all packets 300 on all but the slowest path. Each packet of each stream is assigned 301 a presentation time which is based on the longest required delay. 302 This implies that all sinks must maintain a common time reference of 303 sufficient accuracy, which can be achieved by any of various 304 techniques. 306 This type of architecture is commonly implemented using a central 307 controller that determines path delays and arbitrates buffering 308 delays. 310 2.1.3. Sound Reinforcement 312 Consider the latency (delay) from when a person speaks into a 313 microphone to when their voice emerges from the speaker. If this 314 delay is longer than about 10-15 milliseconds it is noticeable and 315 can make a sound reinforcement system unusable (see slide 6 of 316 [SRP_LATENCY]). (If you have ever tried to speak in the presence of 317 a delayed echo of your voice you may know this experience). 319 Note that the 15ms latency bound includes all parts of the signal 320 path, not just the network, so the network latency must be 321 significantly less than 15ms. 323 In some cases local performers must perform in synchrony with a 324 remote broadcast. In such cases the latencies of the broadcast 325 stream and the local performer must be adjusted to match each other, 326 with a worst case of one video frame (33ms for NTSC video). 328 In cases where audio phase is a consideration, for example beam- 329 forming using multiple speakers, latency requirements can be in the 330 10 microsecond range (1 audio sample at 96kHz). 332 2.1.4. Deterministic Time to Establish Streaming 334 Note: It is still under WG discussion whether this topic (stream 335 startup time) is within scope of DetNet. 337 Some audio systems installed in public environments (airports, 338 hospitals) have unique requirements with regards to health, safety 339 and fire concerns. One such requirement is a maximum of 3 seconds 340 for a system to respond to an emergency detection and begin sending 341 appropriate warning signals and alarms without human intervention. 342 For this requirement to be met, the system must support a bounded and 343 acceptable time from a notification signal to specific stream 344 establishment. For further details see [ISO7240-16]. 346 Similar requirements apply when the system is restarted after a power 347 cycle, cable re-connection, or system reconfiguration. 349 In many cases such re-establishment of streaming state must be 350 achieved by the peer devices themselves, i.e. without a central 351 controller (since such a controller may only be present during 352 initial network configuration). 354 Video systems introduce related requirements, for example when 355 transitioning from one camera feed (video stream) to another (see 356 [STUDIO_IP] and [ESPN_DC2]). 358 2.1.5. Secure Transmission 360 2.1.5.1. Safety 362 Professional audio systems can include amplifiers that are capable of 363 generating hundreds or thousands of watts of audio power which if 364 used incorrectly can cause hearing damage to those in the vicinity. 365 Apart from the usual care required by the systems operators to 366 prevent such incidents, the network traffic that controls these 367 devices must be secured (as with any sensitive application traffic). 369 2.2. Pro Audio Today 371 Some proprietary systems have been created which enable deterministic 372 streams at Layer 3 however they are "engineered networks" which 373 require careful configuration to operate, often require that the 374 system be over-provisioned, and it is implied that all devices on the 375 network voluntarily play by the rules of that network. To enable 376 these industries to successfully transition to an interoperable 377 multi-vendor packet-based infrastructure requires effective open 378 standards, and we believe that establishing relevant IETF standards 379 is a crucial factor. 381 2.3. Pro Audio Future 383 2.3.1. Layer 3 Interconnecting Layer 2 Islands 385 It would be valuable to enable IP to connect multiple Layer 2 LANs. 387 As an example, ESPN recently constructed a state-of-the-art 194,000 388 sq ft, $125 million broadcast studio called DC2. The DC2 network is 389 capable of handling 46 Tbps of throughput with 60,000 simultaneous 390 signals. Inside the facility are 1,100 miles of fiber feeding four 391 audio control rooms (see [ESPN_DC2] ). 393 In designing DC2 they replaced as much point-to-point technology as 394 they could with packet-based technology. They constructed seven 395 individual studios using layer 2 LANS (using IEEE 802.1 AVB) that 396 were entirely effective at routing audio within the LANs. However to 397 interconnect these layer 2 LAN islands together they ended up using 398 dedicated paths in a custom SDN (Software Defined Networking) router 399 because there is no standards-based routing solution available. 401 2.3.2. High Reliability Stream Paths 403 On-air and other live media streams are often backed up with 404 redundant links that seamlessly act to deliver the content when the 405 primary link fails for any reason. In point-to-point systems this is 406 provided by an additional point-to-point link; the analogous 407 requirement in a packet-based system is to provide an alternate path 408 through the network such that no individual link can bring down the 409 system. 411 2.3.3. Integration of Reserved Streams into IT Networks 413 A commonly cited goal of moving to a packet based media 414 infrastructure is that costs can be reduced by using off the shelf, 415 commodity network hardware. In addition, economy of scale can be 416 realized by combining media infrastructure with IT infrastructure. 417 In keeping with these goals, stream reservation technology should be 418 compatible with existing protocols, and not compromise use of the 419 network for best effort (non-time-sensitive) traffic. 421 2.3.4. Use of Unused Reservations by Best-Effort Traffic 423 In cases where stream bandwidth is reserved but not currently used 424 (or is under-utilized) that bandwidth must be available to best- 425 effort (i.e. non-time-sensitive) traffic. For example a single 426 stream may be nailed up (reserved) for specific media content that 427 needs to be presented at different times of the day, ensuring timely 428 delivery of that content, yet in between those times the full 429 bandwidth of the network can be utilized for best-effort tasks such 430 as file transfers. 432 This also addresses a concern of IT network administrators that are 433 considering adding reserved bandwidth traffic to their networks that 434 ("users will reserve large quantities of bandwidth and then never un- 435 reserve it even though they are not using it, and soon the network 436 will have no bandwidth left"). 438 2.3.5. Traffic Segregation 440 Note: It is still under WG discussion whether this topic will be 441 addressed by DetNet. 443 Sink devices may be low cost devices with limited processing power. 444 In order to not overwhelm the CPUs in these devices it is important 445 to limit the amount of traffic that these devices must process. 447 As an example, consider the use of individual seat speakers in a 448 cinema. These speakers are typically required to be cost reduced 449 since the quantities in a single theater can reach hundreds of seats. 450 Discovery protocols alone in a one thousand seat theater can generate 451 enough broadcast traffic to overwhelm a low powered CPU. Thus an 452 installation like this will benefit greatly from some type of traffic 453 segregation that can define groups of seats to reduce traffic within 454 each group. All seats in the theater must still be able to 455 communicate with a central controller. 457 There are many techniques that can be used to support this 458 requirement including (but not limited to) the following examples. 460 2.3.5.1. Packet Forwarding Rules, VLANs and Subnets 462 Packet forwarding rules can be used to eliminate some extraneous 463 streaming traffic from reaching potentially low powered sink devices, 464 however there may be other types of broadcast traffic that should be 465 eliminated using other means for example VLANs or IP subnets. 467 2.3.5.2. Multicast Addressing (IPv4 and IPv6) 469 Multicast addressing is commonly used to keep bandwidth utilization 470 of shared links to a minimum. 472 Because of the MAC Address forwarding nature of Layer 2 bridges it is 473 important that a multicast MAC address is only associated with one 474 stream. This will prevent reservations from forwarding packets from 475 one stream down a path that has no interested sinks simply because 476 there is another stream on that same path that shares the same 477 multicast MAC address. 479 Since each multicast MAC Address can represent 32 different IPv4 480 multicast addresses there must be a process put in place to make sure 481 this does not occur. Requiring use of IPv6 address can achieve this, 482 however due to their continued prevalence, solutions that are 483 effective for IPv4 installations are also required. 485 2.3.6. Latency Optimization by a Central Controller 487 A central network controller might also perform optimizations based 488 on the individual path delays, for example sinks that are closer to 489 the source can inform the controller that they can accept greater 490 latency since they will be buffering packets to match presentation 491 times of farther away sinks. The controller might then move a stream 492 reservation on a short path to a longer path in order to free up 493 bandwidth for other critical streams on that short path. See slides 494 3-5 of [SRP_LATENCY]. 496 Additional optimization can be achieved in cases where sinks have 497 differing latency requirements, for example in a live outdoor concert 498 the speaker sinks have stricter latency requirements than the 499 recording hardware sinks. See slide 7 of [SRP_LATENCY]. 501 2.3.7. Reduced Device Cost Due To Reduced Buffer Memory 503 Device cost can be reduced in a system with guaranteed reservations 504 with a small bounded latency due to the reduced requirements for 505 buffering (i.e. memory) on sink devices. For example, a theme park 506 might broadcast a live event across the globe via a layer 3 protocol; 507 in such cases the size of the buffers required is proportional to the 508 latency bounds and jitter caused by delivery, which depends on the 509 worst case segment of the end-to-end network path. For example on 510 todays open internet the latency is typically unacceptable for audio 511 and video streaming without many seconds of buffering. In such 512 scenarios a single gateway device at the local network that receives 513 the feed from the remote site would provide the expensive buffering 514 required to mask the latency and jitter issues associated with long 515 distance delivery. Sink devices in the local location would have no 516 additional buffering requirements, and thus no additional costs, 517 beyond those required for delivery of local content. The sink device 518 would be receiving the identical packets as those sent by the source 519 and would be unaware that there were any latency or jitter issues 520 along the path. 522 2.4. Pro Audio Asks 524 o Layer 3 routing on top of AVB (and/or other high QoS networks) 526 o Content delivery with bounded, lowest possible latency 528 o IntServ and DiffServ integration with AVB (where practical) 530 o Single network for A/V and IT traffic 532 o Standards-based, interoperable, multi-vendor 534 o IT department friendly 536 o Enterprise-wide networks (e.g. size of San Francisco but not the 537 whole Internet (yet...)) 539 3. Electrical Utilities 541 3.1. Use Case Description 543 Many systems that an electrical utility deploys today rely on high 544 availability and deterministic behavior of the underlying networks. 545 Here we present use cases in Transmission, Generation and 546 Distribution, including key timing and reliability metrics. We also 547 discuss security issues and industry trends which affect the 548 architecture of next generation utility networks 550 3.1.1. Transmission Use Cases 552 3.1.1.1. Protection 554 Protection means not only the protection of human operators but also 555 the protection of the electrical equipment and the preservation of 556 the stability and frequency of the grid. If a fault occurs in the 557 transmission or distribution of electricity then severe damage can 558 occur to human operators, electrical equipment and the grid itself, 559 leading to blackouts. 561 Communication links in conjunction with protection relays are used to 562 selectively isolate faults on high voltage lines, transformers, 563 reactors and other important electrical equipment. The role of the 564 teleprotection system is to selectively disconnect a faulty part by 565 transferring command signals within the shortest possible time. 567 3.1.1.1.1. Key Criteria 569 The key criteria for measuring teleprotection performance are command 570 transmission time, dependability and security. These criteria are 571 defined by the IEC standard 60834 as follows: 573 o Transmission time (Speed): The time between the moment where state 574 changes at the transmitter input and the moment of the 575 corresponding change at the receiver output, including propagation 576 delay. Overall operating time for a teleprotection system 577 includes the time for initiating the command at the transmitting 578 end, the propagation delay over the network (including equipments) 579 and the selection and decision time at the receiving end, 580 including any additional delay due to a noisy environment. 582 o Dependability: The ability to issue and receive valid commands in 583 the presence of interference and/or noise, by minimizing the 584 probability of missing command (PMC). Dependability targets are 585 typically set for a specific bit error rate (BER) level. 587 o Security: The ability to prevent false tripping due to a noisy 588 environment, by minimizing the probability of unwanted commands 589 (PUC). Security targets are also set for a specific bit error 590 rate (BER) level. 592 Additional elements of the the teleprotection system that impact its 593 performance include: 595 o Network bandwidth 597 o Failure recovery capacity (aka resiliency) 599 3.1.1.1.2. Fault Detection and Clearance Timing 601 Most power line equipment can tolerate short circuits or faults for 602 up to approximately five power cycles before sustaining irreversible 603 damage or affecting other segments in the network. This translates 604 to total fault clearance time of 100ms. As a safety precaution, 605 however, actual operation time of protection systems is limited to 606 70- 80 percent of this period, including fault recognition time, 607 command transmission time and line breaker switching time. 609 Some system components, such as large electromechanical switches, 610 require particularly long time to operate and take up the majority of 611 the total clearance time, leaving only a 10ms window for the 612 telecommunications part of the protection scheme, independent of the 613 distance to travel. Given the sensitivity of the issue, new networks 614 impose requirements that are even more stringent: IEC standard 61850 615 limits the transfer time for protection messages to 1/4 - 1/2 cycle 616 or 4 - 8ms (for 60Hz lines) for the most critical messages. 618 3.1.1.1.3. Symmetric Channel Delay 620 Note: It is currently under WG discussion whether symmetric path 621 delays are to be guaranteed by DetNet. 623 Teleprotection channels which are differential must be synchronous, 624 which means that any delays on the transmit and receive paths must 625 match each other. Teleprotection systems ideally support zero 626 asymmetric delay; typical legacy relays can tolerate delay 627 discrepancies of up to 750us. 629 Some tools available for lowering delay variation below this 630 threshold are: 632 o For legacy systems using Time Division Multiplexing (TDM), jitter 633 buffers at the multiplexers on each end of the line can be used to 634 offset delay variation by queuing sent and received packets. The 635 length of the queues must balance the need to regulate the rate of 636 transmission with the need to limit overall delay, as larger 637 buffers result in increased latency. 639 o For jitter-prone IP packet networks, traffic management tools can 640 ensure that the teleprotection signals receive the highest 641 transmission priority to minimize jitter. 643 o Standard packet-based synchronization technologies, such as 644 1588-2008 Precision Time Protocol (PTP) and Synchronous Ethernet 645 (Sync-E), can help keep networks stable by maintaining a highly 646 accurate clock source on the various network devices. 648 3.1.1.1.4. Teleprotection Network Requirements (IEC 61850) 650 The following table captures the main network metrics as based on the 651 IEC 61850 standard. 653 +-----------------------------+-------------------------------------+ 654 | Teleprotection Requirement | Attribute | 655 +-----------------------------+-------------------------------------+ 656 | One way maximum delay | 4-10 ms | 657 | Asymetric delay required | Yes | 658 | Maximum jitter | less than 250 us (750 us for legacy | 659 | | IED) | 660 | Topology | Point to point, point to Multi- | 661 | | point | 662 | Availability | 99.9999 | 663 | precise timing required | Yes | 664 | Recovery time on node | less than 50ms - hitless | 665 | failure | | 666 | performance management | Yes, Mandatory | 667 | Redundancy | Yes | 668 | Packet loss | 0.1% to 1% | 669 +-----------------------------+-------------------------------------+ 671 Table 1: Teleprotection network requirements 673 3.1.1.1.5. Inter-Trip Protection scheme 675 "Inter-tripping" is the signal-controlled tripping of a circuit 676 breaker to complete the isolation of a circuit or piece of apparatus 677 in concert with the tripping of other circuit breakers. 679 +--------------------------------+----------------------------------+ 680 | Inter-Trip protection | Attribute | 681 | Requirement | | 682 +--------------------------------+----------------------------------+ 683 | One way maximum delay | 5 ms | 684 | Asymetric delay required | No | 685 | Maximum jitter | Not critical | 686 | Topology | Point to point, point to Multi- | 687 | | point | 688 | Bandwidth | 64 Kbps | 689 | Availability | 99.9999 | 690 | precise timing required | Yes | 691 | Recovery time on node failure | less than 50ms - hitless | 692 | performance management | Yes, Mandatory | 693 | Redundancy | Yes | 694 | Packet loss | 0.1% | 695 +--------------------------------+----------------------------------+ 697 Table 2: Inter-Trip protection network requirements 699 3.1.1.1.6. Current Differential Protection Scheme 701 Current differential protection is commonly used for line protection, 702 and is typical for protecting parallel circuits. At both end of the 703 lines the current is measured by the differential relays, and both 704 relays will trip the circuit breaker if the current going into the 705 line does not equal the current going out of the line. This type of 706 protection scheme assumes some form of communications being present 707 between the relays at both end of the line, to allow both relays to 708 compare measured current values. Line differential protection 709 schemes assume a very low telecommunications delay between both 710 relays, often as low as 5ms. Moreover, as those systems are often 711 not time-synchronized, they also assume symmetric telecommunications 712 paths with constant delay, which allows comparing current measurement 713 values taken at the exact same time. 715 +----------------------------------+--------------------------------+ 716 | Current Differential protection | Attribute | 717 | Requirement | | 718 +----------------------------------+--------------------------------+ 719 | One way maximum delay | 5 ms | 720 | Asymetric delay Required | Yes | 721 | Maximum jitter | less than 250 us (750us for | 722 | | legacy IED) | 723 | Topology | Point to point, point to | 724 | | Multi-point | 725 | Bandwidth | 64 Kbps | 726 | Availability | 99.9999 | 727 | precise timing required | Yes | 728 | Recovery time on node failure | less than 50ms - hitless | 729 | performance management | Yes, Mandatory | 730 | Redundancy | Yes | 731 | Packet loss | 0.1% | 732 +----------------------------------+--------------------------------+ 734 Table 3: Current Differential Protection metrics 736 3.1.1.1.7. Distance Protection Scheme 738 Distance (Impedance Relay) protection scheme is based on voltage and 739 current measurements. The network metrics are similar (but not 740 identical to) Current Differential protection. 742 +-------------------------------+-----------------------------------+ 743 | Distance protection | Attribute | 744 | Requirement | | 745 +-------------------------------+-----------------------------------+ 746 | One way maximum delay | 5 ms | 747 | Asymetric delay Required | No | 748 | Maximum jitter | Not critical | 749 | Topology | Point to point, point to Multi- | 750 | | point | 751 | Bandwidth | 64 Kbps | 752 | Availability | 99.9999 | 753 | precise timing required | Yes | 754 | Recovery time on node failure | less than 50ms - hitless | 755 | performance management | Yes, Mandatory | 756 | Redundancy | Yes | 757 | Packet loss | 0.1% | 758 +-------------------------------+-----------------------------------+ 760 Table 4: Distance Protection requirements 762 3.1.1.1.8. Inter-Substation Protection Signaling 764 This use case describes the exchange of Sampled Value and/or GOOSE 765 (Generic Object Oriented Substation Events) message between 766 Intelligent Electronic Devices (IED) in two substations for 767 protection and tripping coordination. The two IEDs are in a master- 768 slave mode. 770 The Current Transformer or Voltage Transformer (CT/VT) in one 771 substation sends the sampled analog voltage or current value to the 772 Merging Unit (MU) over hard wire. The MU sends the time-synchronized 773 61850-9-2 sampled values to the slave IED. The slave IED forwards 774 the information to the Master IED in the other substation. The 775 master IED makes the determination (for example based on sampled 776 value differentials) to send a trip command to the originating IED. 777 Once the slave IED/Relay receives the GOOSE trip for breaker 778 tripping, it opens the breaker. It then sends a confirmation message 779 back to the master. All data exchanges between IEDs are either 780 through Sampled Value and/or GOOSE messages. 782 +----------------------------------+--------------------------------+ 783 | Inter-Substation protection | Attribute | 784 | Requirement | | 785 +----------------------------------+--------------------------------+ 786 | One way maximum delay | 5 ms | 787 | Asymetric delay Required | No | 788 | Maximum jitter | Not critical | 789 | Topology | Point to point, point to | 790 | | Multi-point | 791 | Bandwidth | 64 Kbps | 792 | Availability | 99.9999 | 793 | precise timing required | Yes | 794 | Recovery time on node failure | less than 50ms - hitless | 795 | performance management | Yes, Mandatory | 796 | Redundancy | Yes | 797 | Packet loss | 1% | 798 +----------------------------------+--------------------------------+ 800 Table 5: Inter-Substation Protection requirements 802 3.1.1.2. Intra-Substation Process Bus Communications 804 This use case describes the data flow from the CT/VT to the IEDs in 805 the substation via the MU. The CT/VT in the substation send the 806 sampled value (analog voltage or current) to the MU over hard wire. 807 The MU sends the time-synchronized 61850-9-2 sampled values to the 808 IEDs in the substation in GOOSE message format. The GPS Master Clock 809 can send 1PPS or IRIG-B format to the MU through a serial port or 810 IEEE 1588 protocol via a network. Process bus communication using 811 61850 simplifies connectivity within the substation and removes the 812 requirement for multiple serial connections and removes the slow 813 serial bus architectures that are typically used. This also ensures 814 increased flexibility and increased speed with the use of multicast 815 messaging between multiple devices. 817 +----------------------------------+--------------------------------+ 818 | Intra-Substation protection | Attribute | 819 | Requirement | | 820 +----------------------------------+--------------------------------+ 821 | One way maximum delay | 5 ms | 822 | Asymetric delay Required | No | 823 | Maximum jitter | Not critical | 824 | Topology | Point to point, point to | 825 | | Multi-point | 826 | Bandwidth | 64 Kbps | 827 | Availability | 99.9999 | 828 | precise timing required | Yes | 829 | Recovery time on Node failure | less than 50ms - hitless | 830 | performance management | Yes, Mandatory | 831 | Redundancy | Yes - No | 832 | Packet loss | 0.1% | 833 +----------------------------------+--------------------------------+ 835 Table 6: Intra-Substation Protection requirements 837 3.1.1.3. Wide Area Monitoring and Control Systems 839 The application of synchrophasor measurement data from Phasor 840 Measurement Units (PMU) to Wide Area Monitoring and Control Systems 841 promises to provide important new capabilities for improving system 842 stability. Access to PMU data enables more timely situational 843 awareness over larger portions of the grid than what has been 844 possible historically with normal SCADA (Supervisory Control and Data 845 Acquisition) data. Handling the volume and real-time nature of 846 synchrophasor data presents unique challenges for existing 847 application architectures. Wide Area management System (WAMS) makes 848 it possible for the condition of the bulk power system to be observed 849 and understood in real-time so that protective, preventative, or 850 corrective action can be taken. Because of the very high sampling 851 rate of measurements and the strict requirement for time 852 synchronization of the samples, WAMS has stringent telecommunications 853 requirements in an IP network that are captured in the following 854 table: 856 +----------------------+--------------------------------------------+ 857 | WAMS Requirement | Attribute | 858 +----------------------+--------------------------------------------+ 859 | One way maximum | 50 ms | 860 | delay | | 861 | Asymetric delay | No | 862 | Required | | 863 | Maximum jitter | Not critical | 864 | Topology | Point to point, point to Multi-point, | 865 | | Multi-point to Multi-point | 866 | Bandwidth | 100 Kbps | 867 | Availability | 99.9999 | 868 | precise timing | Yes | 869 | required | | 870 | Recovery time on | less than 50ms - hitless | 871 | Node failure | | 872 | performance | Yes, Mandatory | 873 | management | | 874 | Redundancy | Yes | 875 | Packet loss | 1% | 876 +----------------------+--------------------------------------------+ 878 Table 7: WAMS Special Communication Requirements 880 3.1.1.4. IEC 61850 WAN engineering guidelines requirement 881 classification 883 The IEC (International Electrotechnical Commission) has recently 884 published a Technical Report which offers guidelines on how to define 885 and deploy Wide Area Networks for the interconnections of electric 886 substations, generation plants and SCADA operation centers. The IEC 887 61850-90-12 is providing a classification of WAN communication 888 requirements into 4 classes. Table 8 summarizes these requirements: 890 +----------------+------------+------------+------------+-----------+ 891 | WAN | Class WA | Class WB | Class WC | Class WD | 892 | Requirement | | | | | 893 +----------------+------------+------------+------------+-----------+ 894 | Application | EHV (Extra | HV (High | MV (Medium | General | 895 | field | High | Voltage) | Voltage) | purpose | 896 | | Voltage) | | | | 897 | Latency | 5 ms | 10 ms | 100 ms | > 100 ms | 898 | Jitter | 10 us | 100 us | 1 ms | 10 ms | 899 | Latency | 100 us | 1 ms | 10 ms | 100 ms | 900 | Asymetry | | | | | 901 | Time Accuracy | 1 us | 10 us | 100 us | 10 to 100 | 902 | | | | | ms | 903 | Bit Error rate | 10-7 to | 10-5 to | 10-3 | | 904 | | 10-6 | 10-4 | | | 905 | Unavailability | 10-7 to | 10-5 to | 10-3 | | 906 | | 10-6 | 10-4 | | | 907 | Recovery delay | Zero | 50 ms | 5 s | 50 s | 908 | Cyber security | extremely | High | Medium | Medium | 909 | | high | | | | 910 +----------------+------------+------------+------------+-----------+ 912 Table 8: 61850-90-12 Communication Requirements; Courtesy of IEC 914 3.1.2. Generation Use Case 916 The electrical power generation frequency should be maintained within 917 a very narrow band. Deviations from the acceptable frequency range 918 are detected and the required signals are sent to the power plants 919 for frequency regulation. 921 Automatic generation control (AGC) is a system for adjusting the 922 power output of generators at different power plants, in response to 923 changes in the load. 925 +---------------------------------------------------+---------------+ 926 | FCAG (Frequency Control Automatic Generation) | Attribute | 927 | Requirement | | 928 +---------------------------------------------------+---------------+ 929 | One way maximum delay | 500 ms | 930 | Asymetric delay Required | No | 931 | Maximum jitter | Not critical | 932 | Topology | Point to | 933 | | point | 934 | Bandwidth | 20 Kbps | 935 | Availability | 99.999 | 936 | precise timing required | Yes | 937 | Recovery time on Node failure | N/A | 938 | performance management | Yes, | 939 | | Mandatory | 940 | Redundancy | Yes | 941 | Packet loss | 1% | 942 +---------------------------------------------------+---------------+ 944 Table 9: FCAG Communication Requirements 946 3.1.3. Distribution use case 948 3.1.3.1. Fault Location Isolation and Service Restoration (FLISR) 950 Fault Location, Isolation, and Service Restoration (FLISR) refers to 951 the ability to automatically locate the fault, isolate the fault, and 952 restore service in the distribution network. This will likely be the 953 first widespread application of distributed intelligence in the grid. 955 Static power switch status (open/closed) in the network dictates the 956 power flow to secondary substations. Reconfiguring the network in 957 the event of a fault is typically done manually on site to energize/ 958 de-energize alternate paths. Automating the operation of substation 959 switchgear allows the flow of power to be altered automatically under 960 fault conditions. 962 FLISR can be managed centrally from a Distribution Management System 963 (DMS) or executed locally through distributed control via intelligent 964 switches and fault sensors. 966 +----------------------+--------------------------------------------+ 967 | FLISR Requirement | Attribute | 968 +----------------------+--------------------------------------------+ 969 | One way maximum | 80 ms | 970 | delay | | 971 | Asymetric delay | No | 972 | Required | | 973 | Maximum jitter | 40 ms | 974 | Topology | Point to point, point to Multi-point, | 975 | | Multi-point to Multi-point | 976 | Bandwidth | 64 Kbps | 977 | Availability | 99.9999 | 978 | precise timing | Yes | 979 | required | | 980 | Recovery time on | Depends on customer impact | 981 | Node failure | | 982 | performance | Yes, Mandatory | 983 | management | | 984 | Redundancy | Yes | 985 | Packet loss | 0.1% | 986 +----------------------+--------------------------------------------+ 988 Table 10: FLISR Communication Requirements 990 3.2. Electrical Utilities Today 992 Many utilities still rely on complex environments formed of multiple 993 application-specific proprietary networks, including TDM networks. 995 In this kind of environment there is no mixing of OT and IT 996 applications on the same network, and information is siloed between 997 operational areas. 999 Specific calibration of the full chain is required, which is costly. 1001 This kind of environment prevents utility operations from realizing 1002 the operational efficiency benefits, visibility, and functional 1003 integration of operational information across grid applications and 1004 data networks. 1006 In addition, there are many security-related issues as discussed in 1007 the following section. 1009 3.2.1. Security Current Practices and Limitations 1011 Grid monitoring and control devices are already targets for cyber 1012 attacks, and legacy telecommunications protocols have many intrinsic 1013 network-related vulnerabilities. For example, DNP3, Modbus, 1014 PROFIBUS/PROFINET, and other protocols are designed around a common 1015 paradigm of request and respond. Each protocol is designed for a 1016 master device such as an HMI (Human Machine Interface) system to send 1017 commands to subordinate slave devices to retrieve data (reading 1018 inputs) or control (writing to outputs). Because many of these 1019 protocols lack authentication, encryption, or other basic security 1020 measures, they are prone to network-based attacks, allowing a 1021 malicious actor or attacker to utilize the request-and-respond system 1022 as a mechanism for command-and-control like functionality. Specific 1023 security concerns common to most industrial control, including 1024 utility telecommunication protocols include the following: 1026 o Network or transport errors (e.g. malformed packets or excessive 1027 latency) can cause protocol failure. 1029 o Protocol commands may be available that are capable of forcing 1030 slave devices into inoperable states, including powering-off 1031 devices, forcing them into a listen-only state, disabling 1032 alarming. 1034 o Protocol commands may be available that are capable of restarting 1035 communications and otherwise interrupting processes. 1037 o Protocol commands may be available that are capable of clearing, 1038 erasing, or resetting diagnostic information such as counters and 1039 diagnostic registers. 1041 o Protocol commands may be available that are capable of requesting 1042 sensitive information about the controllers, their configurations, 1043 or other need-to-know information. 1045 o Most protocols are application layer protocols transported over 1046 TCP; therefore it is easy to transport commands over non-standard 1047 ports or inject commands into authorized traffic flows. 1049 o Protocol commands may be available that are capable of 1050 broadcasting messages to many devices at once (i.e. a potential 1051 DoS). 1053 o Protocol commands may be available to query the device network to 1054 obtain defined points and their values (i.e. a configuration 1055 scan). 1057 o Protocol commands may be available that will list all available 1058 function codes (i.e. a function scan). 1060 These inherent vulnerabilities, along with increasing connectivity 1061 between IT an OT networks, make network-based attacks very feasible. 1063 Simple injection of malicious protocol commands provides control over 1064 the target process. Altering legitimate protocol traffic can also 1065 alter information about a process and disrupt the legitimate controls 1066 that are in place over that process. A man-in-the-middle attack 1067 could provide both control over a process and misrepresentation of 1068 data back to operator consoles. 1070 3.3. Electrical Utilities Future 1072 The business and technology trends that are sweeping the utility 1073 industry will drastically transform the utility business from the way 1074 it has been for many decades. At the core of many of these changes 1075 is a drive to modernize the electrical grid with an integrated 1076 telecommunications infrastructure. However, interoperability 1077 concerns, legacy networks, disparate tools, and stringent security 1078 requirements all add complexity to the grid transformation. Given 1079 the range and diversity of the requirements that should be addressed 1080 by the next generation telecommunications infrastructure, utilities 1081 need to adopt a holistic architectural approach to integrate the 1082 electrical grid with digital telecommunications across the entire 1083 power delivery chain. 1085 The key to modernizing grid telecommunications is to provide a 1086 common, adaptable, multi-service network infrastructure for the 1087 entire utility organization. Such a network serves as the platform 1088 for current capabilities while enabling future expansion of the 1089 network to accommodate new applications and services. 1091 To meet this diverse set of requirements, both today and in the 1092 future, the next generation utility telecommunnications network will 1093 be based on open-standards-based IP architecture. An end-to-end IP 1094 architecture takes advantage of nearly three decades of IP technology 1095 development, facilitating interoperability across disparate networks 1096 and devices, as it has been already demonstrated in many mission- 1097 critical and highly secure networks. 1099 IPv6 is seen as a future telecommunications technology for the Smart 1100 Grid; the IEC (International Electrotechnical Commission) and 1101 different National Committees have mandated a specific adhoc group 1102 (AHG8) to define the migration strategy to IPv6 for all the IEC TC57 1103 power automation standards. 1105 3.3.1. Migration to Packet-Switched Network 1107 Throughout the world, utilities are increasingly planning for a 1108 future based on smart grid applications requiring advanced 1109 telecommunications systems. Many of these applications utilize 1110 packet connectivity for communicating information and control signals 1111 across the utility's Wide Area Network (WAN), made possible by 1112 technologies such as multiprotocol label switching (MPLS). The data 1113 that traverses the utility WAN includes: 1115 o Grid monitoring, control, and protection data 1117 o Non-control grid data (e.g. asset data for condition-based 1118 monitoring) 1120 o Physical safety and security data (e.g. voice and video) 1122 o Remote worker access to corporate applications (voice, maps, 1123 schematics, etc.) 1125 o Field area network backhaul for smart metering, and distribution 1126 grid management 1128 o Enterprise traffic (email, collaboration tools, business 1129 applications) 1131 WANs support this wide variety of traffic to and from substations, 1132 the transmission and distribution grid, generation sites, between 1133 control centers, and between work locations and data centers. To 1134 maintain this rapidly expanding set of applications, many utilities 1135 are taking steps to evolve present time-division multiplexing (TDM) 1136 based and frame relay infrastructures to packet systems. Packet- 1137 based networks are designed to provide greater functionalities and 1138 higher levels of service for applications, while continuing to 1139 deliver reliability and deterministic (real-time) traffic support. 1141 3.3.2. Telecommunications Trends 1143 These general telecommunications topics are in addition to the use 1144 cases that have been addressed so far. These include both current 1145 and future telecommunications related topics that should be factored 1146 into the network architecture and design. 1148 3.3.2.1. General Telecommunications Requirements 1150 o IP Connectivity everywhere 1152 o Monitoring services everywhere and from different remote centers 1154 o Move services to a virtual data center 1156 o Unify access to applications / information from the corporate 1157 network 1159 o Unify services 1161 o Unified Communications Solutions 1163 o Mix of fiber and microwave technologies - obsolescence of SONET/ 1164 SDH or TDM 1166 o Standardize grid telecommunications protocol to opened standard to 1167 ensure interoperability 1169 o Reliable Telecommunications for Transmission and Distribution 1170 Substations 1172 o IEEE 1588 time synchronization Client / Server Capabilities 1174 o Integration of Multicast Design 1176 o QoS Requirements Mapping 1178 o Enable Future Network Expansion 1180 o Substation Network Resilience 1182 o Fast Convergence Design 1184 o Scalable Headend Design 1186 o Define Service Level Agreements (SLA) and Enable SLA Monitoring 1188 o Integration of 3G/4G Technologies and future technologies 1190 o Ethernet Connectivity for Station Bus Architecture 1192 o Ethernet Connectivity for Process Bus Architecture 1194 o Protection, teleprotection and PMU (Phaser Measurement Unit) on IP 1196 3.3.2.2. Specific Network topologies of Smart Grid Applications 1198 Utilities often have very large private telecommunications networks. 1199 It covers an entire territory / country. The main purpose of the 1200 network, until now, has been to support transmission network 1201 monitoring, control, and automation, remote control of generation 1202 sites, and providing FCAPS (Fault, Configuration, Accounting, 1203 Performance, Security) services from centralized network operation 1204 centers. 1206 Going forward, one network will support operation and maintenance of 1207 electrical networks (generation, transmission, and distribution), 1208 voice and data services for ten of thousands of employees and for 1209 exchange with neighboring interconnections, and administrative 1210 services. To meet those requirements, utility may deploy several 1211 physical networks leveraging different technologies across the 1212 country: an optical network and a microwave network for instance. 1213 Each protection and automatism system between two points has two 1214 telecommunications circuits, one on each network. Path diversity 1215 between two substations is key. Regardless of the event type 1216 (hurricane, ice storm, etc.), one path shall stay available so the 1217 system can still operate. 1219 In the optical network, signals are transmitted over more than tens 1220 of thousands of circuits using fiber optic links, microwave and 1221 telephone cables. This network is the nervous system of the 1222 utility's power transmission operations. The optical network 1223 represents ten of thousands of km of cable deployed along the power 1224 lines, with individual runs as long as 280 km. 1226 3.3.2.3. Precision Time Protocol 1228 Some utilities do not use GPS clocks in generation substations. One 1229 of the main reasons is that some of the generation plants are 30 to 1230 50 meters deep under ground and the GPS signal can be weak and 1231 unreliable. Instead, atomic clocks are used. Clocks are 1232 synchronized amongst each other. Rubidium clocks provide clock and 1233 1ms timestamps for IRIG-B. 1235 Some companies plan to transition to the Precision Time Protocol 1236 (PTP, [IEEE1588]), distributing the synchronization signal over the 1237 IP/MPLS network. PTP provides a mechanism for synchronizing the 1238 clocks of participating nodes to a high degree of accuracy and 1239 precision. 1241 PTP operates based on the following assumptions: 1243 It is assumed that the network eliminates cyclic forwarding of PTP 1244 messages within each communication path (e.g. by using a spanning 1245 tree protocol). 1247 PTP is tolerant of an occasional missed message, duplicated 1248 message, or message that arrived out of order. However, PTP 1249 assumes that such impairments are relatively rare. 1251 PTP was designed assuming a multicast communication model, however 1252 PTP also supports a unicast communication model as long as the 1253 behavior of the protocol is preserved. 1255 Like all message-based time transfer protocols, PTP time accuracy 1256 is degraded by delay asymmetry in the paths taken by event 1257 messages. Asymmetry is not detectable by PTP, however, if such 1258 delays are known a priori, PTP can correct for asymmetry. 1260 IEC 61850 will recommend the use of the IEEE PTP 1588 Utility Profile 1261 (as defined in [IEC62439-3:2012] Annex B) which offers the support of 1262 redundant attachment of clocks to Parallel Redundancy Protcol (PRP) 1263 and High-availability Seamless Redundancy (HSR) networks. 1265 3.3.3. Security Trends in Utility Networks 1267 Although advanced telecommunications networks can assist in 1268 transforming the energy industry by playing a critical role in 1269 maintaining high levels of reliability, performance, and 1270 manageability, they also introduce the need for an integrated 1271 security infrastructure. Many of the technologies being deployed to 1272 support smart grid projects such as smart meters and sensors can 1273 increase the vulnerability of the grid to attack. Top security 1274 concerns for utilities migrating to an intelligent smart grid 1275 telecommunications platform center on the following trends: 1277 o Integration of distributed energy resources 1279 o Proliferation of digital devices to enable management, automation, 1280 protection, and control 1282 o Regulatory mandates to comply with standards for critical 1283 infrastructure protection 1285 o Migration to new systems for outage management, distribution 1286 automation, condition-based maintenance, load forecasting, and 1287 smart metering 1289 o Demand for new levels of customer service and energy management 1291 This development of a diverse set of networks to support the 1292 integration of microgrids, open-access energy competition, and the 1293 use of network-controlled devices is driving the need for a converged 1294 security infrastructure for all participants in the smart grid, 1295 including utilities, energy service providers, large commercial and 1296 industrial, as well as residential customers. Securing the assets of 1297 electric power delivery systems (from the control center to the 1298 substation, to the feeders and down to customer meters) requires an 1299 end-to-end security infrastructure that protects the myriad of 1300 telecommunications assets used to operate, monitor, and control power 1301 flow and measurement. 1303 "Cyber security" refers to all the security issues in automation and 1304 telecommunications that affect any functions related to the operation 1305 of the electric power systems. Specifically, it involves the 1306 concepts of: 1308 o Integrity : data cannot be altered undetectably 1310 o Authenticity : the telecommunications parties involved must be 1311 validated as genuine 1313 o Authorization : only requests and commands from the authorized 1314 users can be accepted by the system 1316 o Confidentiality : data must not be accessible to any 1317 unauthenticated users 1319 When designing and deploying new smart grid devices and 1320 telecommunications systems, it is imperative to understand the 1321 various impacts of these new components under a variety of attack 1322 situations on the power grid. Consequences of a cyber attack on the 1323 grid telecommunications network can be catastrophic. This is why 1324 security for smart grid is not just an ad hoc feature or product, 1325 it's a complete framework integrating both physical and Cyber 1326 security requirements and covering the entire smart grid networks 1327 from generation to distribution. Security has therefore become one 1328 of the main foundations of the utility telecom network architecture 1329 and must be considered at every layer with a defense-in-depth 1330 approach. Migrating to IP based protocols is key to address these 1331 challenges for two reasons: 1333 o IP enables a rich set of features and capabilities to enhance the 1334 security posture 1336 o IP is based on open standards, which allows interoperability 1337 between different vendors and products, driving down the costs 1338 associated with implementing security solutions in OT networks. 1340 Securing OT (Operation technology) telecommunications over packet- 1341 switched IP networks follow the same principles that are foundational 1342 for securing the IT infrastructure, i.e., consideration must be given 1343 to enforcing electronic access control for both person-to-machine and 1344 machine-to-machine communications, and providing the appropriate 1345 levels of data privacy, device and platform integrity, and threat 1346 detection and mitigation. 1348 3.4. Electrical Utilities Asks 1350 o Mixed L2 and L3 topologies 1352 o Deterministic behavior 1354 o Bounded latency and jitter 1356 o High availability, low recovery time 1358 o Redundancy, low packet loss 1360 o Precise timing 1362 o Centralized computing of deterministic paths 1364 o Distributed configuration may also be useful 1366 4. Building Automation Systems 1368 4.1. Use Case Description 1370 A Building Automation System (BAS) manages equipment and sensors in a 1371 building for improving residents' comfort, reducing energy 1372 consumption, and responding to failures and emergencies. For 1373 example, the BAS measures the temperature of a room using sensors and 1374 then controls the HVAC (heating, ventilating, and air conditioning) 1375 to maintain a set temperature and minimize energy consumption. 1377 A BAS primarily performs the following functions: 1379 o Periodically measures states of devices, for example humidity and 1380 illuminance of rooms, open/close state of doors, FAN speed, etc. 1382 o Stores the measured data. 1384 o Provides the measured data to BAS systems and operators. 1386 o Generates alarms for abnormal state of devices. 1388 o Controls devices (e.g. turn off room lights at 10:00 PM). 1390 4.2. Building Automation Systems Today 1391 4.2.1. BAS Architecture 1393 A typical BAS architecture of today is shown in Figure 1. 1395 +----------------------------+ 1396 | | 1397 | BMS HMI | 1398 | | | | 1399 | +----------------------+ | 1400 | | Management Network | | 1401 | +----------------------+ | 1402 | | | | 1403 | LC LC | 1404 | | | | 1405 | +----------------------+ | 1406 | | Field Network | | 1407 | +----------------------+ | 1408 | | | | | | 1409 | Dev Dev Dev Dev | 1410 | | 1411 +----------------------------+ 1413 BMS := Building Management Server 1414 HMI := Human Machine Interface 1415 LC := Local Controller 1417 Figure 1: BAS architecture 1419 There are typically two layers of network in a BAS. The upper one is 1420 called the Management Network and the lower one is called the Field 1421 Network. In management networks an IP-based communication protocol 1422 is used, while in field networks non-IP based communication protocols 1423 ("field protocols") are mainly used. Field networks have specific 1424 timing requirements, whereas management networks can be best-effort. 1426 A Human Machine Interface (HMI) is typically a desktop PC used by 1427 operators to monitor and display device states, send device control 1428 commands to Local Controllers (LCs), and configure building schedules 1429 (for example "turn off all room lights in the building at 10:00 PM"). 1431 A Building Management Server (BMS) performs the following operations. 1433 o Collect and store device states from LCs at regular intervals. 1435 o Send control values to LCs according to a building schedule. 1437 o Send an alarm signal to operators if it detects abnormal devices 1438 states. 1440 The BMS and HMI communicate with LCs via IP-based "management 1441 protocols" (see standards [bacnetip], [knx]). 1443 A LC is typically a Programmable Logic Controller (PLC) which is 1444 connected to several tens or hundreds of devices using "field 1445 protocols". An LC performs the following kinds of operations: 1447 o Measure device states and provide the information to BMS or HMI. 1449 o Send control values to devices, unilaterally or as part of a 1450 feedback control loop. 1452 There are many field protocols used today; some are standards-based 1453 and others are proprietary (see standards [lontalk], [modbus], 1454 [profibus] and [flnet]). The result is that BASs have multiple MAC/ 1455 PHY modules and interfaces. This makes BASs more expensive, slower 1456 to develop, and can result in "vendor lock-in" with multiple types of 1457 management applications. 1459 4.2.2. BAS Deployment Model 1461 An example BAS for medium or large buildings is shown in Figure 2. 1462 The physical layout spans multiple floors, and there is a monitoring 1463 room where the BAS management entities are located. Each floor will 1464 have one or more LCs depending upon the number of devices connected 1465 to the field network. 1467 +--------------------------------------------------+ 1468 | Floor 3 | 1469 | +----LC~~~~+~~~~~+~~~~~+ | 1470 | | | | | | 1471 | | Dev Dev Dev | 1472 | | | 1473 |--- | ------------------------------------------| 1474 | | Floor 2 | 1475 | +----LC~~~~+~~~~~+~~~~~+ Field Network | 1476 | | | | | | 1477 | | Dev Dev Dev | 1478 | | | 1479 |--- | ------------------------------------------| 1480 | | Floor 1 | 1481 | +----LC~~~~+~~~~~+~~~~~+ +-----------------| 1482 | | | | | | Monitoring Room | 1483 | | Dev Dev Dev | | 1484 | | | BMS HMI | 1485 | | Management Network | | | | 1486 | +--------------------------------+-----+ | 1487 | | | 1488 +--------------------------------------------------+ 1490 Figure 2: BAS Deployment model for Medium/Large Buildings 1492 Each LC is connected to the monitoring room via the Management 1493 network, and the management functions are performed within the 1494 building. In most cases, fast Ethernet (e.g. 100BASE-T) is used for 1495 the management network. Since the management network is non- 1496 realtime, use of Ethernet without quality of service is sufficient 1497 for today's deployment. 1499 In the field network a variety of physical interfaces such as RS232C 1500 and RS485 are used, which have specific timing requirements. Thus if 1501 a field network is to be replaced with an Ethernet or wireless 1502 network, such networks must support time-critical deterministic 1503 flows. 1505 In Figure 3, another deployment model is presented in which the 1506 management system is hosted remotely. This is becoming popular for 1507 small office and residential buildings in which a standalone 1508 monitoring system is not cost-effective. 1510 +---------------+ 1511 | Remote Center | 1512 | | 1513 | BMS HMI | 1514 +------------------------------------+ | | | | 1515 | Floor 2 | | +---+---+ | 1516 | +----LC~~~~+~~~~~+ Field Network| | | | 1517 | | | | | | Router | 1518 | | Dev Dev | +-------|-------+ 1519 | | | | 1520 |--- | ------------------------------| | 1521 | | Floor 1 | | 1522 | +----LC~~~~+~~~~~+ | | 1523 | | | | | | 1524 | | Dev Dev | | 1525 | | | | 1526 | | Management Network | WAN | 1527 | +------------------------Router-------------+ 1528 | | 1529 +------------------------------------+ 1531 Figure 3: Deployment model for Small Buildings 1533 Some interoperability is possible today in the Management Network, 1534 but not in today's field networks due to their non-IP-based design. 1536 4.2.3. Use Cases for Field Networks 1538 Below are use cases for Environmental Monitoring, Fire Detection, and 1539 Feedback Control, and their implications for field network 1540 performance. 1542 4.2.3.1. Environmental Monitoring 1544 The BMS polls each LC at a maximum measurement interval of 100ms (for 1545 example to draw a historical chart of 1 second granularity with a 10x 1546 sampling interval) and then performs the operations as specified by 1547 the operator. Each LC needs to measure each of its several hundred 1548 sensors once per measurement interval. Latency is not critical in 1549 this scenario as long as all sensor values are completed in the 1550 measurement interval. Availability is expected to be 99.999 %. 1552 4.2.3.2. Fire Detection 1554 On detection of a fire, the BMS must stop the HVAC, close the fire 1555 shutters, turn on the fire sprinklers, send an alarm, etc. There are 1556 typically ~10s of sensors per LC that BMS needs to manage. In this 1557 scenario the measurement interval is 10-50ms, the communication delay 1558 is 10ms, and the availability must be 99.9999 %. 1560 4.2.3.3. Feedback Control 1562 BAS systems utilize feedback control in various ways; the most time- 1563 critial is control of DC motors, which require a short feedback 1564 interval (1-5ms) with low communication delay (10ms) and jitter 1565 (1ms). The feedback interval depends on the characteristics of the 1566 device and a target quality of control value. There are typically 1567 ~10s of such devices per LC. 1569 Communication delay is expected to be less than 10 ms, jitter less 1570 than 1 sec while the availability must be 99.9999% . 1572 4.2.4. Security Considerations 1574 When BAS field networks were developed it was assumed that the field 1575 networks would always be physically isolated from external networks 1576 and therefore security was not a concern. In today's world many BASs 1577 are managed remotely and are thus connected to shared IP networks and 1578 so security is definitely a concern, yet security features are not 1579 available in the majority of BAS field network deployments . 1581 The management network, being an IP-based network, has the protocols 1582 available to enable network security, but in practice many BAS 1583 systems do not implement even the available security features such as 1584 device authentication or encryption for data in transit. 1586 4.3. BAS Future 1588 In the future we expect more fine-grained environmental monitoring 1589 and lower energy consumption, which will require more sensors and 1590 devices, thus requiring larger and more complex building networks. 1592 We expect building networks to be connected to or converged with 1593 other networks (Enterprise network, Home network, and Internet). 1595 Therefore better facilities for network management, control, 1596 reliability and security are critical in order to improve resident 1597 and operator convenience and comfort. For example the ability to 1598 monitor and control building devices via the internet would enable 1599 (for example) control of room lights or HVAC from a resident's 1600 desktop PC or phone application. 1602 4.4. BAS Asks 1604 The community would like to see an interoperable protocol 1605 specification that can satisfy the timing, security, availability and 1606 QoS constraints described above, such that the resulting converged 1607 network can replace the disparate field networks. Ideally this 1608 connectivity could extend to the open Internet. 1610 This would imply an architecture that can guarantee 1612 o Low communication delays (from <10ms to 100ms in a network of 1613 several hundred devices) 1615 o Low jitter (< 1 ms) 1617 o Tight feedback intervals (1ms - 10ms) 1619 o High network availability (up to 99.9999% ) 1621 o Availability of network data in disaster scenario 1623 o Authentication between management and field devices (both local 1624 and remote) 1626 o Integrity and data origin authentication of communication data 1627 between field and management devices 1629 o Confidentiality of data when communicated to a remote device 1631 5. Wireless for Industrial 1633 5.1. Use Case Description 1635 Wireless networks are useful for industrial applications, for example 1636 when portable, fast-moving or rotating objects are involved, and for 1637 the resource-constrained devices found in the Internet of Things 1638 (IoT). 1640 Such network-connected sensors, actuators, control loops (etc.) 1641 typically require that the underlying network support real-time 1642 quality of service (QoS), as well as specific classes of other 1643 network properties such as reliability, redundancy, and security. 1645 These networks may also contain very large numbers of devices, for 1646 example for factories, "big data" acquisition, and the IoT. Given 1647 the large numbers of devices installed, and the potential 1648 pervasiveness of the IoT, this is a huge and very cost-sensitive 1649 market. For example, a 1% cost reduction in some areas could save 1650 $100B 1652 5.1.1. Network Convergence using 6TiSCH 1654 Some wireless network technologies support real-time QoS, and are 1655 thus useful for these kinds of networks, but others do not. For 1656 example WiFi is pervasive but does not provide guaranteed timing or 1657 delivery of packets, and thus is not useful in this context. 1659 In this use case we focus on one specific wireless network technology 1660 which does provide the required deterministic QoS, which is "IPv6 1661 over the TSCH mode of IEEE 802.15.4e" (6TiSCH, where TSCH stands for 1662 "Time-Slotted Channel Hopping", see [I-D.ietf-6tisch-architecture], 1663 [IEEE802154], [IEEE802154e], and [RFC7554]). 1665 There are other deterministic wireless busses and networks available 1666 today, however they are imcompatible with each other, and 1667 incompatible with IP traffic (for example [ISA100], [WirelessHART]). 1669 Thus the primary goal of this use case is to apply 6TiSH as a 1670 converged IP- and standards-based wireless network for industrial 1671 applications, i.e. to replace multiple proprietary and/or 1672 incompatible wireless networking and wireless network management 1673 standards. 1675 5.1.2. Common Protocol Development for 6TiSCH 1677 Today there are a number of protocols required by 6TiSCH which are 1678 still in development, and a second intent of this use case is to 1679 highlight the ways in which these "missing" protocols share goals in 1680 common with DetNet. Thus it is possible that some of the protocol 1681 technology developed for DetNet will also be applicable to 6TiSCH. 1683 These protocol goals are identified here, along with their 1684 relationship to DetNet. It is likely that ultimately the resulting 1685 protocols will not be identical, but will share design principles 1686 which contribute to the eficiency of enabling both DetNet and 6TiSCH. 1688 One such commonality is that although at a different time scale, in 1689 both TSN [IEEE802.1TSNTG] and TSCH a packet crosses the network from 1690 node to node follows a precise schedule, as a train that leaves 1691 intermediate stations at precise times along its path. This kind of 1692 operation reduces collisions, saves energy, and enables engineering 1693 the network for deterministic properties. 1695 Another commonality is remote monitoring and scheduling management of 1696 a TSCH network by a Path Computation Element (PCE) and Network 1697 Management Entity (NME). The PCE/NME manage timeslots and device 1698 resources in a manner that minimizes the interaction with and the 1699 load placed on resource-constrained devices. For example, a tiny IoT 1700 device may have just enough buffers to store one or a few IPv6 1701 packets, and will have limited bandwidth between peers such that it 1702 can maintain only a small amount of peer information, and will not be 1703 able to store many packets waiting to be forwarded. It is 1704 advantageous then for it to only be required to carry out the 1705 specific behavior assigned to it by the PCE/NME (as opposed to 1706 maintaining its own IP stack, for example). 1708 Note: Current WG discussion indicates that some peer-to-peer 1709 communication must be assumed, i.e. the PCE may communicate only 1710 indirectly with any given device, enabling hierarchical configuration 1711 of the system. 1713 6TiSCH depends on [PCE] and [I-D.finn-detnet-architecture]. 1715 6TiSCH also depends on the fact that DetNet will maintain consistency 1716 with [IEEE802.1TSNTG]. 1718 5.2. Wireless Industrial Today 1720 Today industrial wireless is accomplished using multiple 1721 deterministic wireless networks which are incompatible with each 1722 other and with IP traffic. 1724 6TiSCH is not yet fully specified, so it cannot be used in today's 1725 applications. 1727 5.3. Wireless Industrial Future 1729 5.3.1. Unified Wireless Network and Management 1731 We expect DetNet and 6TiSCH together to enable converged transport of 1732 deterministic and best-effort traffic flows between real-time 1733 industrial devices and wide area networks via IP routing. A high 1734 level view of a basic such network is shown in Figure 4. 1736 ---+-------- ............ ------------ 1737 | External Network | 1738 | +-----+ 1739 +-----+ | NME | 1740 | | LLN Border | | 1741 | | router +-----+ 1742 +-----+ 1743 o o o 1744 o o o o 1745 o o LLN o o o 1746 o o o o 1747 o 1749 Figure 4: Basic 6TiSCH Network 1751 Figure 5 shows a backbone router federating multiple synchronized 1752 6TiSCH subnets into a single subnet connected to the external 1753 network. 1755 ---+-------- ............ ------------ 1756 | External Network | 1757 | +-----+ 1758 | +-----+ | NME | 1759 +-----+ | +-----+ | | 1760 | | Router | | PCE | +-----+ 1761 | | +--| | 1762 +-----+ +-----+ 1763 | | 1764 | Subnet Backbone | 1765 +--------------------+------------------+ 1766 | | | 1767 +-----+ +-----+ +-----+ 1768 | | Backbone | | Backbone | | Backbone 1769 o | | router | | router | | router 1770 +-----+ +-----+ +-----+ 1771 o o o o o 1772 o o o o o o o o o o o 1773 o o o LLN o o o o 1774 o o o o o o o o o o o o 1776 Figure 5: Extended 6TiSCH Network 1778 The backbone router must ensure end-to-end deterministic behavior 1779 between the LLN and the backbone. We would like to see this 1780 accomplished in conformance with the work done in 1781 [I-D.finn-detnet-architecture] with respect to Layer-3 aspects of 1782 deterministic networks that span multiple Layer-2 domains. 1784 The PCE must compute a deterministic path end-to-end across the TSCH 1785 network and IEEE802.1 TSN Ethernet backbone, and DetNet protocols are 1786 expected to enable end-to-end deterministic forwarding. 1788 +-----+ 1789 | IoT | 1790 | G/W | 1791 +-----+ 1792 ^ <---- Elimination 1793 | | 1794 Track branch | | 1795 +-------+ +--------+ Subnet Backbone 1796 | | 1797 +--|--+ +--|--+ 1798 | | | Backbone | | | Backbone 1799 o | | | router | | | router 1800 +--/--+ +--|--+ 1801 o / o o---o----/ o 1802 o o---o--/ o o o o o 1803 o \ / o o LLN o 1804 o v <---- Replication 1805 o 1807 Figure 6: 6TiSCH Network with PRE 1809 5.3.1.1. PCE and 6TiSCH ARQ Retries 1811 Note: The possible use of ARQ techniques in DetNet is currently 1812 considered a possible design alternative. 1814 6TiSCH uses the IEEE802.15.4 Automatic Repeat-reQuest (ARQ) mechanism 1815 to provide higher reliability of packet delivery. ARQ is related to 1816 packet replication and elimination because there are two independent 1817 paths for packets to arrive at the destination, and if an expected 1818 packed does not arrive on one path then it checks for the packet on 1819 the second path. 1821 Although to date this mechanism is only used by wireless networks, 1822 this may be a technique that would be appropriate for DetNet and so 1823 aspects of the enabling protocol could be co-developed. 1825 For example, in Figure 6, a Track is laid out from a field device in 1826 a 6TiSCH network to an IoT gateway that is located on a IEEE802.1 TSN 1827 backbone. 1829 In ARQ the Replication function in the field device sends a copy of 1830 each packet over two different branches, and the PCE schedules each 1831 hop of both branches so that the two copies arrive in due time at the 1832 gateway. In case of a loss on one branch, hopefully the other copy 1833 of the packet still arrives within the allocated time. If two copies 1834 make it to the IoT gateway, the Elimination function in the gateway 1835 ignores the extra packet and presents only one copy to upper layers. 1837 At each 6TiSCH hop along the Track, the PCE may schedule more than 1838 one timeSlot for a packet, so as to support Layer-2 retries (ARQ). 1840 In current deployments, a TSCH Track does not necessarily support PRE 1841 but is systematically multi-path. This means that a Track is 1842 scheduled so as to ensure that each hop has at least two forwarding 1843 solutions, and the forwarding decision is to try the preferred one 1844 and use the other in case of Layer-2 transmission failure as detected 1845 by ARQ. 1847 5.3.2. Schedule Management by a PCE 1849 A common feature of 6TiSCH and DetNet is the action of a PCE to 1850 configure paths through the network. Specifically, what is needed is 1851 a protocol and data model that the PCE will use to get/set the 1852 relevant configuration from/to the devices, as well as perform 1853 operations on the devices. We expect that this protocol will be 1854 developed by DetNet with consideration for its reuse by 6TiSCH. The 1855 remainder of this section provides a bit more context from the 6TiSCH 1856 side. 1858 5.3.2.1. PCE Commands and 6TiSCH CoAP Requests 1860 The 6TiSCH device does not expect to place the request for bandwidth 1861 between itself and another device in the network. Rather, an 1862 operation control system invoked through a human interface specifies 1863 the required traffic specification and the end nodes (in terms of 1864 latency and reliability). Based on this information, the PCE must 1865 compute a path between the end nodes and provision the network with 1866 per-flow state that describes the per-hop operation for a given 1867 packet, the corresponding timeslots, and the flow identification that 1868 enables recognizing that a certain packet belongs to a certain path, 1869 etc. 1871 For a static configuration that serves a certain purpose for a long 1872 period of time, it is expected that a node will be provisioned in one 1873 shot with a full schedule, which incorporates the aggregation of its 1874 behavior for multiple paths. 6TiSCH expects that the programing of 1875 the schedule will be done over COAP as discussed in 1876 [I-D.ietf-6tisch-coap]. 1878 6TiSCH expects that the PCE commands will be mapped back and forth 1879 into CoAP by a gateway function at the edge of the 6TiSCH network. 1880 For instance, it is possible that a mapping entity on the backbone 1881 transforms a non-CoAP protocol such as PCEP into the RESTful 1882 interfaces that the 6TiSCH devices support. This architecture will 1883 be refined to comply with DetNet [I-D.finn-detnet-architecture] when 1884 the work is formalized. Related information about 6TiSCH can be 1885 found at [I-D.ietf-6tisch-6top-interface] and RPL [RFC6550]. 1887 A protocol may be used to update the state in the devices during 1888 runtime, for example if it appears that a path through the network 1889 has ceased to perform as expected, but in 6TiSCH that flow was not 1890 designed and no protocol was selected. We would like to see DetNet 1891 define the appropriate end-to-end protocols to be used in that case. 1892 The implication is that these state updates take place once the 1893 system is configured and running, i.e. they are not limited to the 1894 initial communication of the configuration of the system. 1896 A "slotFrame" is the base object that a PCE would manipulate to 1897 program a schedule into an LLN node ([I-D.ietf-6tisch-architecture]). 1899 We would like to see the PCE read energy data from devices, and 1900 compute paths that will implement policies on how energy in devices 1901 is consumed, for instance to ensure that the spent energy does not 1902 exceeded the available energy over a period of time. Note: this 1903 statement implies that an extensible protocol for communicating 1904 device info to the PCE and enabling the PCE to act on it will be part 1905 of the DetNet architecture, however for subnets with specific 1906 protocols (e.g. CoAP) a gateway may be required. 1908 6TiSCH devices can discover their neighbors over the radio using a 1909 mechanism such as beacons, but even though the neighbor information 1910 is available in the 6TiSCH interface data model, 6TiSCH does not 1911 describe a protocol to proactively push the neighborhood information 1912 to a PCE. We would like to see DetNet define such a protocol; one 1913 possible design alternative is that it could operate over CoAP, 1914 alternatively it could be converted to/from CoAP by a gateway. We 1915 would like to see such a protocol carry multiple metrics, for example 1916 similar to those used for RPL operations [RFC6551] 1918 5.3.2.2. 6TiSCH IP Interface 1920 "6top" ([I-D.wang-6tisch-6top-sublayer]) is a logical link control 1921 sitting between the IP layer and the TSCH MAC layer which provides 1922 the link abstraction that is required for IP operations. The 6top 1923 data model and management interfaces are further discussed in 1924 [I-D.ietf-6tisch-6top-interface] and [I-D.ietf-6tisch-coap]. 1926 An IP packet that is sent along a 6TiSCH path uses the Differentiated 1927 Services Per-Hop-Behavior Group called Deterministic Forwarding, as 1928 described in [I-D.svshah-tsvwg-deterministic-forwarding]. 1930 5.3.3. 6TiSCH Security Considerations 1932 On top of the classical requirements for protection of control 1933 signaling, it must be noted that 6TiSCH networks operate on limited 1934 resources that can be depleted rapidly in a DoS attack on the system, 1935 for instance by placing a rogue device in the network, or by 1936 obtaining management control and setting up unexpected additional 1937 paths. 1939 5.4. Wireless Industrial Asks 1941 6TiSCH depends on DetNet to define: 1943 o Configuration (state) and operations for deterministic paths 1945 o End-to-end protocols for deterministic forwarding (tagging, IP) 1947 o Protocol for packet replication and elimination 1949 6. Cellular Radio 1951 6.1. Use Case Description 1953 This use case describes the application of deterministic networking 1954 in the context of cellular telecom transport networks. Important 1955 elements include time synchronization, clock distribution, and ways 1956 of establishing time-sensitive streams for both Layer-2 and Layer-3 1957 user plane traffic. 1959 6.1.1. Network Architecture 1961 Figure 7 illustrates a typical 3GPP-defined cellular network 1962 architecture, which includes "Fronthaul" and "Midhaul" network 1963 segments. The "Fronthaul" is the network connecting base stations 1964 (baseband processing units) to the remote radio heads (antennas). 1965 The "Midhaul" is the network inter-connecting base stations (or small 1966 cell sites). 1968 In Figure 7 "eNB" ("E-UTRAN Node B") is the hardware that is 1969 connected to the mobile phone network which communicates directly 1970 with mobile handsets ([TS36300]). 1972 Y (remote radio heads (antennas)) 1973 \ 1974 Y__ \.--. .--. +------+ 1975 \_( `. +---+ _(Back`. | 3GPP | 1976 Y------( Front )----|eNB|----( Haul )----| core | 1977 ( ` .Haul ) +---+ ( ` . ) ) | netw | 1978 /`--(___.-' \ `--(___.-' +------+ 1979 Y_/ / \.--. \ 1980 Y_/ _( Mid`. \ 1981 ( Haul ) \ 1982 ( ` . ) ) \ 1983 `--(___.-'\_____+---+ (small cell sites) 1984 \ |SCe|__Y 1985 +---+ +---+ 1986 Y__|eNB|__Y 1987 +---+ 1988 Y_/ \_Y ("local" radios) 1990 Figure 7: Generic 3GPP-based Cellular Network Architecture 1992 6.1.2. Delay Constraints 1994 The available processing time for Fronthaul networking overhead is 1995 limited to the available time after the baseband processing of the 1996 radio frame has completed. For example in Long Term Evolution (LTE) 1997 radio, processing of a radio frame is allocated 3ms but typically the 1998 processing uses most of it, allowing only a small fraction to be used 1999 by the Fronthaul network (e.g. up to 250us one-way delay, though the 2000 existing spec ([NGMN-fronth]) supports delay only up to 100us). This 2001 ultimately determines the distance the remote radio heads can be 2002 located from the base stations (e.g., 100us equals roughly 20 km of 2003 optical fiber-based transport). Allocation options of the available 2004 time budget between processing and transport are under heavy 2005 discussions in the mobile industry. 2007 For packet-based transport the allocated transport time (e.g. CPRI 2008 would allow for 100us delay [CPRI]) is consumed by all nodes and 2009 buffering between the remote radio head and the baseband processing 2010 unit, plus the distance-incurred delay. 2012 The baseband processing time and the available "delay budget" for the 2013 fronthaul is likely to change in the forthcoming "5G" due to reduced 2014 radio round trip times and other architectural and service 2015 requirements [NGMN]. 2017 [METIS] documents the fundamental challenges as well as overall 2018 technical goals of the future 5G mobile and wireless system as the 2019 starting point. These future systems should support much higher data 2020 volumes and rates and significantly lower end-to-end latency for 100x 2021 more connected devices (at similar cost and energy consumption levels 2022 as today's system). 2024 For Midhaul connections, delay constraints are driven by Inter-Site 2025 radio functions like Coordinated Multipoint Processing (CoMP, see 2026 [CoMP]). CoMP reception and transmission is a framework in which 2027 multiple geographically distributed antenna nodes cooperate to 2028 improve the performance of the users served in the common cooperation 2029 area. The design principal of CoMP is to extend the current single- 2030 cell to multi-UE (User Equipment) transmission to a multi-cell-to- 2031 multi-UEs transmission by base station cooperation. 2033 CoMP has delay-sensitive performance parameters, which are "midhaul 2034 latency" and "CSI (Channel State Information) reporting and 2035 accuracy". The essential feature of CoMP is signaling between eNBs, 2036 so Midhaul latency is the dominating limitation of CoMP performance. 2037 Generally, CoMP can benefit from coordinated scheduling (either 2038 distributed or centralized) of different cells if the signaling delay 2039 between eNBs is within 1-10ms. This delay requirement is both rigid 2040 and absolute because any uncertainty in delay will degrade the 2041 performance significantly. 2043 Inter-site CoMP is one of the key requirements for 5G and is also a 2044 near-term goal for the current 4.5G network architecture. 2046 6.1.3. Time Synchronization Constraints 2048 Fronthaul time synchronization requirements are given by [TS25104], 2049 [TS36104], [TS36211], and [TS36133]. These can be summarized for the 2050 current 3GPP LTE-based networks as: 2052 Delay Accuracy: 2053 +-8ns (i.e. +-1/32 Tc, where Tc is the UMTS Chip time of 1/3.84 2054 MHz) resulting in a round trip accuracy of +-16ns. The value is 2055 this low to meet the 3GPP Timing Alignment Error (TAE) measurement 2056 requirements. Note: performance guarantees of low nanosecond 2057 values such as these are considered to be below the DetNet layer - 2058 it is assumed that the underlying implementation, e.g. the 2059 hardware, will provide sufficient support (e.g. buffering) to 2060 enable this level of accuracy. These values are maintained in the 2061 use case to give an indication of the overall application. 2063 Timing Alignment Error: 2064 Timing Alignment Error (TAE) is problematic to Fronthaul networks 2065 and must be minimized. If the transport network cannot guarantee 2066 low enough TAE then additional buffering has to be introduced at 2067 the edges of the network to buffer out the jitter. Buffering is 2068 not desirable as it reduces the total available delay budget. 2069 Packet Delay Variation (PDV) requirements can be derived from TAE 2070 for packet based Fronthaul networks. 2072 * For multiple input multiple output (MIMO) or TX diversity 2073 transmissions, at each carrier frequency, TAE shall not exceed 2074 65 ns (i.e. 1/4 Tc). 2076 * For intra-band contiguous carrier aggregation, with or without 2077 MIMO or TX diversity, TAE shall not exceed 130 ns (i.e. 1/2 2078 Tc). 2080 * For intra-band non-contiguous carrier aggregation, with or 2081 without MIMO or TX diversity, TAE shall not exceed 260 ns (i.e. 2082 one Tc). 2084 * For inter-band carrier aggregation, with or without MIMO or TX 2085 diversity, TAE shall not exceed 260 ns. 2087 Transport link contribution to radio frequency error: 2088 +-2 PPB. This value is considered to be "available" for the 2089 Fronthaul link out of the total 50 PPB budget reserved for the 2090 radio interface. Note: the reason that the transport link 2091 contributes to radio frequency error is as follows. The current 2092 way of doing Fronthaul is from the radio unit to remote radio head 2093 directly. The remote radio head is essentially a passive device 2094 (without buffering etc.) The transport drives the antenna 2095 directly by feeding it with samples and everything the transport 2096 adds will be introduced to radio as-is. So if the transport 2097 causes additional frequency error that shows immediately on the 2098 radio as well. Note: performance guarantees of low nanosecond 2099 values such as these are considered to be below the DetNet layer - 2100 it is assumed that the underlying implementation, e.g. the 2101 hardware, will provide sufficient support to enable this level of 2102 performance. These values are maintained in the use case to give 2103 an indication of the overall application. 2105 The above listed time synchronization requirements are difficult to 2106 meet with point-to-point connected networks, and more difficult when 2107 the network includes multiple hops. It is expected that networks 2108 must include buffering at the ends of the connections as imposed by 2109 the jitter requirements, since trying to meet the jitter requirements 2110 in every intermediate node is likely to be too costly. However, 2111 every measure to reduce jitter and delay on the path makes it easier 2112 to meet the end-to-end requirements. 2114 In order to meet the timing requirements both senders and receivers 2115 must remain time synchronized, demanding very accurate clock 2116 distribution, for example support for IEEE 1588 transparent clocks in 2117 every intermediate node. 2119 In cellular networks from the LTE radio era onward, phase 2120 synchronization is needed in addition to frequency synchronization 2121 ([TS36300], [TS23401]). 2123 6.1.4. Transport Loss Constraints 2125 Fronthaul and Midhaul networks assume almost error-free transport. 2126 Errors can result in a reset of the radio interfaces, which can cause 2127 reduced throughput or broken radio connectivity for mobile customers. 2129 For packetized Fronthaul and Midhaul connections packet loss may be 2130 caused by BER, congestion, or network failure scenarios. Current 2131 tools for elminating packet loss for Fronthaul and Midhaul networks 2132 have serious challenges, for example retransmitting lost packets and/ 2133 or using forward error correction (FEC) to circumvent bit errors is 2134 practically impossible due to the additional delay incurred. Using 2135 redundant streams for better guarantees for delivery is also 2136 practically impossible in many cases due to high bandwidth 2137 requirements of Fronthaul and Midhaul networks. Protection switching 2138 is also a candidate but current technologies for the path switch are 2139 too slow to avoid reset of mobile interfaces. 2141 Fronthaul links are assumed to be symmetric, and all Fronthaul 2142 streams (i.e. those carrying radio data) have equal priority and 2143 cannot delay or pre-empt each other. This implies that the network 2144 must guarantee that each time-sensitive flow meets their schedule. 2146 6.1.5. Security Considerations 2148 Establishing time-sensitive streams in the network entails reserving 2149 networking resources for long periods of time. It is important that 2150 these reservation requests be authenticated to prevent malicious 2151 reservation attempts from hostile nodes (or accidental 2152 misconfiguration). This is particularly important in the case where 2153 the reservation requests span administrative domains. Furthermore, 2154 the reservation information itself should be digitally signed to 2155 reduce the risk of a legitimate node pushing a stale or hostile 2156 configuration into another networking node. 2158 Note: This is considered important for the security policy of the 2159 network, but does not affect the core DetNet architecture and design. 2161 6.2. Cellular Radio Networks Today 2163 6.2.1. Fronthaul 2165 Today's Fronthaul networks typically consist of: 2167 o Dedicated point-to-point fiber connection is common 2169 o Proprietary protocols and framings 2171 o Custom equipment and no real networking 2173 Current solutions for Fronthaul are direct optical cables or 2174 Wavelength-Division Multiplexing (WDM) connections. 2176 6.2.2. Midhaul and Backhaul 2178 Today's Midhaul and Backhaul networks typically consist of: 2180 o Mostly normal IP networks, MPLS-TP, etc. 2182 o Clock distribution and sync using 1588 and SyncE 2184 Telecommunication networks in the Mid- and Backhaul are already 2185 heading towards transport networks where precise time synchronization 2186 support is one of the basic building blocks. While the transport 2187 networks themselves have practically transitioned to all-IP packet- 2188 based networks to meet the bandwidth and cost requirements, highly 2189 accurate clock distribution has become a challenge. 2191 In the past, Mid- and Backhaul connections were typically based on 2192 Time Division Multiplexing (TDM-based) and provided frequency 2193 synchronization capabilities as a part of the transport media. 2194 Alternatively other technologies such as Global Positioning System 2195 (GPS) or Synchronous Ethernet (SyncE) are used [SyncE]. 2197 Both Ethernet and IP/MPLS [RFC3031] (and PseudoWires (PWE) [RFC3985] 2198 for legacy transport support) have become popular tools to build and 2199 manage new all-IP Radio Access Networks (RANs) 2200 [I-D.kh-spring-ip-ran-use-case]. Although various timing and 2201 synchronization optimizations have already been proposed and 2202 implemented including 1588 PTP enhancements 2203 [I-D.ietf-tictoc-1588overmpls] and [I-D.ietf-mpls-residence-time], 2204 these solution are not necessarily sufficient for the forthcoming RAN 2205 architectures nor do they guarantee the more stringent time- 2206 synchronization requirements such as [CPRI]. 2208 There are also existing solutions for TDM over IP such as [RFC5087] 2209 and [RFC4553], as well as TDM over Ethernet transports such as 2210 [RFC5086]. 2212 6.3. Cellular Radio Networks Future 2214 Future Cellular Radio Networks will be based on a mix of different 2215 xHaul networks (xHaul = front-, mid- and backhaul), and future 2216 transport networks should be able to support all of them 2217 simultaneously. It is already envisioned today that: 2219 o Not all "cellular radio network" traffic will be IP, for example 2220 some will remain at Layer 2 (e.g. Ethernet based). DetNet 2221 solutions must address all traffic types (Layer 2, Layer 3) with 2222 the same tools and allow their transport simultaneously. 2224 o All form of xHaul networks will need some form of DetNet 2225 solutions. For example with the advent of 5G some Backhaul 2226 traffic will also have DetNet requirements (e.g. traffic belonging 2227 to time-critical 5G applications). 2229 We would like to see the following in future Cellular Radio networks: 2231 o Unified standards-based transport protocols and standard 2232 networking equipment that can make use of underlying deterministic 2233 link-layer services 2235 o Unified and standards-based network management systems and 2236 protocols in all parts of the network (including Fronthaul) 2238 New radio access network deployment models and architectures may 2239 require time- sensitive networking services with strict requirements 2240 on other parts of the network that previously were not considered to 2241 be packetized at all. Time and synchronization support are already 2242 topical for Backhaul and Midhaul packet networks [MEF] and are 2243 becoming a real issue for Fronthaul networks also. Specifically in 2244 Fronthaul networks the timing and synchronization requirements can be 2245 extreme for packet based technologies, for example, on the order of 2246 sub +-20 ns packet delay variation (PDV) and frequency accuracy of 2247 +0.002 PPM [Fronthaul]. 2249 The actual transport protocols and/or solutions to establish required 2250 transport "circuits" (pinned-down paths) for Fronthaul traffic are 2251 still undefined. Those are likely to include (but are not limited 2252 to) solutions directly over Ethernet, over IP, and using MPLS/ 2253 PseudoWire transport. 2255 Even the current time-sensitive networking features may not be 2256 sufficient for Fronthaul traffic. Therefore, having specific 2257 profiles that take the requirements of Fronthaul into account is 2258 desirable [IEEE8021CM]. 2260 Interesting and important work for time-sensitive networking has been 2261 done for Ethernet [TSNTG], which specifies the use of IEEE 1588 time 2262 precision protocol (PTP) [IEEE1588] in the context of IEEE 802.1D and 2263 IEEE 802.1Q. [IEEE8021AS] specifies a Layer 2 time synchronizing 2264 service, and other specifications such as IEEE 1722 [IEEE1722] 2265 specify Ethernet-based Layer-2 transport for time-sensitive streams. 2267 New promising work seeks to enable the transport of time-sensitive 2268 fronthaul streams in Ethernet bridged networks [IEEE8021CM]. 2269 Analogous to IEEE 1722 there is an ongoing standardization effort to 2270 define the Layer-2 transport encapsulation format for transporting 2271 radio over Ethernet (RoE) in the IEEE 1904.3 Task Force [IEEE19043]. 2273 All-IP RANs and xHhaul networks would benefit from time 2274 synchronization and time-sensitive transport services. Although 2275 Ethernet appears to be the unifying technology for the transport, 2276 there is still a disconnect providing Layer 3 services. The protocol 2277 stack typically has a number of layers below the Ethernet Layer 2 2278 that shows up to the Layer 3 IP transport. It is not uncommon that 2279 on top of the lowest layer (optical) transport there is the first 2280 layer of Ethernet followed one or more layers of MPLS, PseudoWires 2281 and/or other tunneling protocols finally carrying the Ethernet layer 2282 visible to the user plane IP traffic. 2284 While there are existing technologies to establish circuits through 2285 the routed and switched networks (especially in MPLS/PWE space), 2286 there is still no way to signal the time synchronization and time- 2287 sensitive stream requirements/reservations for Layer-3 flows in a way 2288 that addresses the entire transport stack, including the Ethernet 2289 layers that need to be configured. 2291 Furthermore, not all "user plane" traffic will be IP. Therefore, the 2292 same solution also must address the use cases where the user plane 2293 traffic is a different layer, for example Ethernet frames. 2295 There is existing work describing the problem statement 2296 [I-D.finn-detnet-problem-statement] and the architecture 2297 [I-D.finn-detnet-architecture] for deterministic networking (DetNet) 2298 that targets solutions for time-sensitive (IP/transport) streams with 2299 deterministic properties over Ethernet-based switched networks. 2301 6.4. Cellular Radio Networks Asks 2303 A standard for data plane transport specification which is: 2305 o Unified among all xHauls (meaning that different flows with 2306 diverse DetNet requirements can coexist in the same network and 2307 traverse the same nodes without interfering with each other) 2309 o Deployed in a highly deterministic network environment 2311 A standard for data flow information models that are: 2313 o Aware of the time sensitivity and constraints of the target 2314 networking environment 2316 o Aware of underlying deterministic networking services (e.g., on 2317 the Ethernet layer) 2319 7. Industrial M2M 2321 7.1. Use Case Description 2323 Industrial Automation in general refers to automation of 2324 manufacturing, quality control and material processing. In this 2325 "machine to machine" (M2M) use case we consider machine units in a 2326 plant floor which periodically exchange data with upstream or 2327 downstream machine modules and/or a supervisory controller within a 2328 local area network. 2330 The actors of M2M communication are Programmable Logic Controllers 2331 (PLCs). Communication between PLCs and between PLCs and the 2332 supervisory PLC (S-PLC) is achieved via critical control/data streams 2333 Figure 8. 2335 S (Sensor) 2336 \ +-----+ 2337 PLC__ \.--. .--. ---| MES | 2338 \_( `. _( `./ +-----+ 2339 A------( Local )-------------( L2 ) 2340 ( Net ) ( Net ) +-------+ 2341 /`--(___.-' `--(___.-' ----| S-PLC | 2342 S_/ / PLC .--. / +-------+ 2343 A_/ \_( `. 2344 (Actuator) ( Local ) 2345 ( Net ) 2346 /`--(___.-'\ 2347 / \ A 2348 S A 2350 Figure 8: Current Generic Industrial M2M Network Architecture 2352 This use case focuses on PLC-related communications; communication to 2353 Manufacturing-Execution-Systems (MESs) are not addressed. 2355 This use case covers only critical control/data streams; non-critical 2356 traffic between industrial automation applications (such as 2357 communication of state, configuration, set-up, and database 2358 communication) are adequately served by currently available 2359 prioritizing techniques. Such traffic can use up to 80% of the total 2360 bandwidth required. There is also a subset of non-time-critical 2361 traffic that must be reliable even though it is not time sensitive. 2363 In this use case the primary need for deterministic networking is to 2364 provide end-to-end delivery of M2M messages within specific timing 2365 constraints, for example in closed loop automation control. Today 2366 this level of determinism is provided by proprietary networking 2367 technologies. In addition, standard networking technologies are used 2368 to connect the local network to remote industrial automation sites, 2369 e.g. over an enterprise or metro network which also carries other 2370 types of traffic. Therefore, flows that should be forwarded with 2371 deterministic guarantees need to be sustained regardless of the 2372 amount of other flows in those networks. 2374 7.2. Industrial M2M Communication Today 2376 Today, proprietary networks fulfill the needed timing and 2377 availability for M2M networks. 2379 The network topologies used today by industrial automation are 2380 similar to those used by telecom networks: Daisy Chain, Ring, Hub and 2381 Spoke, and Comb (a subset of Daisy Chain). 2383 PLC-related control/data streams are transmitted periodically and 2384 carry either a pre-configured payload or a payload configured during 2385 runtime. 2387 Some industrial applications require time synchronization at the end 2388 nodes. For such time-coordinated PLCs, accuracy of 1 microsecond is 2389 required. Even in the case of "non-time-coordinated" PLCs time sync 2390 may be needed e.g. for timestamping of sensor data. 2392 Industrial network scenarios require advanced security solutions. 2393 Many of the current industrial production networks are physically 2394 separated. Preventing critical flows from be leaked outside a domain 2395 is handled today by filtering policies that are typically enforced in 2396 firewalls. 2398 7.2.1. Transport Parameters 2400 The Cycle Time defines the frequency of message(s) between industrial 2401 actors. The Cycle Time is application dependent, in the range of 1ms 2402 - 100ms for critical control/data streams. 2404 Because industrial applications assume deterministic transport for 2405 critical Control-Data-Stream parameters (instead of defining latency 2406 and delay variation parameters) it is sufficient to fulfill the upper 2407 bound of latency (maximum latency). The underlying networking 2408 infrastructure must ensure a maximum end-to-end delivery time of 2409 messages in the range of 100 microseconds to 50 milliseconds 2410 depending on the control loop application. 2412 The bandwidth requirements of control/data streams are usually 2413 calculated directly from the bytes-per-cycle parameter of the control 2414 loop. For PLC-to-PLC communication one can expect 2 - 32 streams 2415 with packet size in the range of 100 - 700 bytes. For S-PLC to PLCs 2416 the number of streams is higher - up to 256 streams. Usually no more 2417 than 20% of available bandwidth is used for critical control/data 2418 streams. In today's networks 1Gbps links are commonly used. 2420 Most PLC control loops are rather tolerant of packet loss, however 2421 critical control/data streams accept no more than 1 packet loss per 2422 consecutive communication cycle (i.e. if a packet gets lost in cycle 2423 "n", then the next cycle ("n+1") must be lossless). After two or 2424 more consecutive packet losses the network may be considered to be 2425 "down" by the Application. 2427 As network downtime may impact the whole production system the 2428 required network availability is rather high (99,999%). 2430 Based on the above parameters we expect that some form of redundancy 2431 will be required for M2M communications, however any individual 2432 solution depends on several parameters including cycle time, delivery 2433 time, etc. 2435 7.2.2. Stream Creation and Destruction 2437 In an industrial environment, critical control/data streams are 2438 created rather infrequently, on the order of ~10 times per day / week 2439 / month. Most of these critical control/data streams get created at 2440 machine startup, however flexibility is also needed during runtime, 2441 for example when adding or removing a machine. Going forward as 2442 production systems become more flexible, we expect a significant 2443 increase in the rate at which streams are created, changed and 2444 destroyed. 2446 7.3. Industrial M2M Future 2448 We would like to see a converged IP-standards-based network with 2449 deterministic properties that can satisfy the timing, security and 2450 reliability constraints described above. Today's proprietary 2451 networks could then be interfaced to such a network via gateways or, 2452 in the case of new installations, devices could be connected directly 2453 to the converged network. 2455 For this use case we expect time synchronization accuracy on the 2456 order of 1us. 2458 7.4. Industrial M2M Asks 2460 o Converged IP-based network 2462 o Deterministic behavior (bounded latency and jitter ) 2464 o High availability (presumably through redundancy) (99.999 %) 2466 o Low message delivery time (100us - 50ms) 2468 o Low packet loss (burstless, 0.1-1 %) 2470 o Security (e.g. prevent critical flows from being leaked between 2471 physically separated networks) 2473 8. Use Case Common Elements 2475 Looking at the use cases collectively, the following common desires 2476 for the DetNet-based networks of the future emerge: 2478 o Open standards-based network (replace various proprietary 2479 networks, reduce cost, create multi-vendor market) 2481 o Centrally administered (though such administration may be 2482 distributed for scale and resiliency) 2484 o Integrates L2 (bridged) and L3 (routed) environments (independent 2485 of the Link layer, e.g. can be used with Ethernet, 6TiSCH, etc.) 2487 o Carries both deterministic and best-effort traffic (guaranteed 2488 end-to-end delivery of deterministic flows, deterministic flows 2489 isolated from each other and from best-effort traffic congestion, 2490 unused deterministic BW available to best-effort traffic) 2492 o Ability to add or remove systems from the network with minimal, 2493 bounded service interruption (applications include replacement of 2494 failed devices as well as plug and play) 2496 o Uses standardized data flow information models capable of 2497 expressing deterministic properties (models express device 2498 capabilities, flow properties. Protocols for pushing models from 2499 controller to devices, devices to controller) 2501 o Scalable size (long distances (many km) and short distances 2502 (within a single machine), many hops (radio repeaters, microwave 2503 links, fiber links...) and short hops (single machine)) 2505 o Scalable timing parameters and accuracy (bounded latency, 2506 guaranteed worst case maximum, minimum. Low latency, e.g. control 2507 loops may be less than 1ms, but larger for wide area networks) 2509 o High availability (99.9999 percent up time requested, but may be 2510 up to twelve 9s) 2512 o Reliability, redundancy (lives at stake) 2514 o Security (from failures, attackers, misbehaving devices - 2515 sensitive to both packet content and arrival time) 2517 9. Use Cases Explicitly Out of Scope for DetNet 2519 This section contains use case text that has been determined to be 2520 outside of the scope of the present DetNet work. 2522 9.1. DetNet Scope Limitations 2524 The scope of DetNet is deliberately limited to specific use cases 2525 that are consistent with the WG charter, subject to the 2526 interpretation of the WG. At the time the DetNet Use Cases were 2527 solicited and provided by the authors the scope of DetNet was not 2528 clearly defined, and as that clarity has emerged, certain of the use 2529 cases have been determined to be outside the scope of the present 2530 DetNet work. Such text has been moved into this section to clarify 2531 that these use cases will not be supported by the DetNet work. 2533 The text in this section was moved here based on the following 2534 "exclusion" principles. Or, as an alternative to moving all such 2535 text to this section, some draft text has been modified in situ to 2536 reflect these same principles. 2538 The following principles have been established to clarify the scope 2539 of the present DetNet work. 2541 o The scope of network addressed by DetNet is limited to networks 2542 that can be centrally controlled, i.e. an "enterprise" aka 2543 "corporate" network. This explicitly excludes "the open 2544 Internet". 2546 o Maintaining synchronized time across a DetNet network is crucial 2547 to its operation, however DetNet assumes that time is to be 2548 maintained using other means, for example (but not limited to) 2549 Precision Time Protocol ([IEEE1588]). A use case may state the 2550 accuracy and reliability that it expects from the DetNet network 2551 as part of a whole system, however it is understood that such 2552 timing properties are not guaranteed by DetNet itself. It is 2553 currently an open question as to whether DetNet protocols will 2554 include a way for an application to communicate such timing 2555 expectations to the network, and if so whether they would be 2556 expected to materially affect the performance they would receive 2557 from the network as a result. 2559 9.2. Internet-based Applications 2561 9.2.1. Use Case Description 2563 There are many applications that communicate across the open Internet 2564 that could benefit from guaranteed delivery and bounded latency. The 2565 following are some representative examples. 2567 9.2.1.1. Media Content Delivery 2569 Media content delivery continues to be an important use of the 2570 Internet, yet users often experience poor quality audio and video due 2571 to the delay and jitter inherent in today's Internet. 2573 9.2.1.2. Online Gaming 2575 Online gaming is a significant part of the gaming market, however 2576 latency can degrade the end user experience. For example "First 2577 Person Shooter" (FPS) games are highly delay-sensitive. 2579 9.2.1.3. Virtual Reality 2581 Virtual reality (VR) has many commercial applications including real 2582 estate presentations, remote medical procedures, and so on. Low 2583 latency is critical to interacting with the virtual world because 2584 perceptual delays can cause motion sickness. 2586 9.2.2. Internet-Based Applications Today 2588 Internet service today is by definition "best effort", with no 2589 guarantees on delivery or bandwidth. 2591 9.2.3. Internet-Based Applications Future 2593 We imagine an Internet from which we will be able to play a video 2594 without glitches and play games without lag. 2596 For online gaming, the maximum round-trip delay can be 100ms and 2597 stricter for FPS gaming which can be 10-50ms. Transport delay is the 2598 dominate part with a 5-20ms budget. 2600 For VR, 1-10ms maximum delay is needed and total network budget is 2601 1-5ms if doing remote VR. 2603 Flow identification can be used for gaming and VR, i.e. it can 2604 recognize a critical flow and provide appropriate latency bounds. 2606 9.2.4. Internet-Based Applications Asks 2608 o Unified control and management protocols to handle time-critical 2609 data flow 2611 o Application-aware flow filtering mechanism to recognize the timing 2612 critical flow without doing 5-tuple matching 2614 o Unified control plane to provide low latency service on Layer-3 2615 without changing the data plane 2617 o OAM system and protocols which can help to provide E2E-delay 2618 sensitive service provisioning 2620 9.3. Pro Audio and Video - Digital Rights Management (DRM) 2622 This section was moved here because this is considered a Link layer 2623 topic, not direct responsibility of DetNet. 2625 Digital Rights Management (DRM) is very important to the audio and 2626 video industries. Any time protected content is introduced into a 2627 network there are DRM concerns that must be maintained (see 2628 [CONTENT_PROTECTION]). Many aspects of DRM are outside the scope of 2629 network technology, however there are cases when a secure link 2630 supporting authentication and encryption is required by content 2631 owners to carry their audio or video content when it is outside their 2632 own secure environment (for example see [DCI]). 2634 As an example, two techniques are Digital Transmission Content 2635 Protection (DTCP) and High-Bandwidth Digital Content Protection 2636 (HDCP). HDCP content is not approved for retransmission within any 2637 other type of DRM, while DTCP may be retransmitted under HDCP. 2638 Therefore if the source of a stream is outside of the network and it 2639 uses HDCP protection it is only allowed to be placed on the network 2640 with that same HDCP protection. 2642 9.4. Pro Audio and Video - Link Aggregation 2644 Note: The term "Link Aggregation" is used here as defined by the text 2645 in the following paragraph, i.e. not following a more common Network 2646 Industry definition. Current WG consensus is that this item won't be 2647 directly supported by the DetNet architecture, for example because it 2648 implies guarantee of in-order delivery of packets which conflicts 2649 with the core goal of achieving the lowest possible latency. 2651 For transmitting streams that require more bandwidth than a single 2652 link in the target network can support, link aggregation is a 2653 technique for combining (aggregating) the bandwidth available on 2654 multiple physical links to create a single logical link of the 2655 required bandwidth. However, if aggregation is to be used, the 2656 network controller (or equivalent) must be able to determine the 2657 maximum latency of any path through the aggregate link. 2659 10. Acknowledgments 2661 10.1. Pro Audio 2663 This section was derived from draft-gunther-detnet-proaudio-req-01. 2665 The editors would like to acknowledge the help of the following 2666 individuals and the companies they represent: 2668 Jeff Koftinoff, Meyer Sound 2670 Jouni Korhonen, Associate Technical Director, Broadcom 2672 Pascal Thubert, CTAO, Cisco 2674 Kieran Tyrrell, Sienda New Media Technologies GmbH 2676 10.2. Utility Telecom 2678 This section was derived from draft-wetterwald-detnet-utilities-reqs- 2679 02. 2681 Faramarz Maghsoodlou, Ph. D. IoT Connected Industries and Energy 2682 Practice Cisco 2684 Pascal Thubert, CTAO Cisco 2686 10.3. Building Automation Systems 2688 This section was derived from draft-bas-usecase-detnet-00. 2690 10.4. Wireless for Industrial 2692 This section was derived from draft-thubert-6tisch-4detnet-01. 2694 This specification derives from the 6TiSCH architecture, which is the 2695 result of multiple interactions, in particular during the 6TiSCH 2696 (bi)Weekly Interim call, relayed through the 6TiSCH mailing list at 2697 the IETF. 2699 The authors wish to thank: Kris Pister, Thomas Watteyne, Xavier 2700 Vilajosana, Qin Wang, Tom Phinney, Robert Assimiti, Michael 2701 Richardson, Zhuo Chen, Malisa Vucinic, Alfredo Grieco, Martin Turon, 2702 Dominique Barthel, Elvis Vogli, Guillaume Gaillard, Herman Storey, 2703 Maria Rita Palattella, Nicola Accettura, Patrick Wetterwald, Pouria 2704 Zand, Raghuram Sudhaakar, and Shitanshu Shah for their participation 2705 and various contributions. 2707 10.5. Cellular Radio 2709 This section was derived from draft-korhonen-detnet-telreq-00. 2711 10.6. Industrial M2M 2713 The authors would like to thank Feng Chen and Marcel Kiessling for 2714 their comments and suggestions. 2716 10.7. Internet Applications and CoMP 2718 This section was derived from draft-zha-detnet-use-case-00. 2720 This document has benefited from reviews, suggestions, comments and 2721 proposed text provided by the following members, listed in 2722 alphabetical order: Jing Huang, Junru Lin, Lehong Niu and Oilver 2723 Huang. 2725 11. Informative References 2727 [ACE] IETF, "Authentication and Authorization for Constrained 2728 Environments", . 2731 [bacnetip] 2732 ASHRAE, "Annex J to ANSI/ASHRAE 135-1995 - BACnet/IP", 2733 January 1999. 2735 [CCAMP] IETF, "Common Control and Measurement Plane", 2736 . 2738 [CoMP] NGMN Alliance, "RAN EVOLUTION PROJECT COMP EVALUATION AND 2739 ENHANCEMENT", NGMN Alliance NGMN_RANEV_D3_CoMP_Evaluation_ 2740 and_Enhancement_v2.0, March 2015, 2741 . 2744 [CONTENT_PROTECTION] 2745 Olsen, D., "1722a Content Protection", 2012, 2746 . 2749 [CPRI] CPRI Cooperation, "Common Public Radio Interface (CPRI); 2750 Interface Specification", CPRI Specification V6.1, July 2751 2014, . 2754 [CPRI-transp] 2755 CPRI TWG, "CPRI requirements for Ethernet Fronthaul", 2756 November 2015, 2757 . 2760 [DCI] Digital Cinema Initiatives, LLC, "DCI Specification, 2761 Version 1.2", 2012, . 2763 [DICE] IETF, "DTLS In Constrained Environments", 2764 . 2766 [EA12] Evans, P. and M. Annunziata, "Industrial Internet: Pushing 2767 the Boundaries of Minds and Machines", November 2012. 2769 [ESPN_DC2] 2770 Daley, D., "ESPN's DC2 Scales AVB Large", 2014, 2771 . 2774 [flnet] Japan Electrical Manufacturers' Association, "JEMA 1479 - 2775 English Edition", September 2012. 2777 [Fronthaul] 2778 Chen, D. and T. Mustala, "Ethernet Fronthaul 2779 Considerations", IEEE 1904.3, February 2015, 2780 . 2783 [HART] www.hartcomm.org, "Highway Addressable remote Transducer, 2784 a group of specifications for industrial process and 2785 control devices administered by the HART Foundation". 2787 [I-D.finn-detnet-architecture] 2788 Finn, N., Thubert, P., and M. Teener, "Deterministic 2789 Networking Architecture", draft-finn-detnet- 2790 architecture-04 (work in progress), March 2016. 2792 [I-D.finn-detnet-problem-statement] 2793 Finn, N. and P. Thubert, "Deterministic Networking Problem 2794 Statement", draft-finn-detnet-problem-statement-05 (work 2795 in progress), March 2016. 2797 [I-D.ietf-6tisch-6top-interface] 2798 Wang, Q. and X. Vilajosana, "6TiSCH Operation Sublayer 2799 (6top) Interface", draft-ietf-6tisch-6top-interface-04 2800 (work in progress), July 2015. 2802 [I-D.ietf-6tisch-architecture] 2803 Thubert, P., "An Architecture for IPv6 over the TSCH mode 2804 of IEEE 802.15.4", draft-ietf-6tisch-architecture-10 (work 2805 in progress), June 2016. 2807 [I-D.ietf-6tisch-coap] 2808 Sudhaakar, R. and P. Zand, "6TiSCH Resource Management and 2809 Interaction using CoAP", draft-ietf-6tisch-coap-03 (work 2810 in progress), March 2015. 2812 [I-D.ietf-6tisch-terminology] 2813 Palattella, M., Thubert, P., Watteyne, T., and Q. Wang, 2814 "Terminology in IPv6 over the TSCH mode of IEEE 2815 802.15.4e", draft-ietf-6tisch-terminology-07 (work in 2816 progress), March 2016. 2818 [I-D.ietf-ipv6-multilink-subnets] 2819 Thaler, D. and C. Huitema, "Multi-link Subnet Support in 2820 IPv6", draft-ietf-ipv6-multilink-subnets-00 (work in 2821 progress), July 2002. 2823 [I-D.ietf-mpls-residence-time] 2824 Mirsky, G., Ruffini, S., Gray, E., Drake, J., Bryant, S., 2825 and S. Vainshtein, "Residence Time Measurement in MPLS 2826 network", draft-ietf-mpls-residence-time-09 (work in 2827 progress), April 2016. 2829 [I-D.ietf-roll-rpl-industrial-applicability] 2830 Phinney, T., Thubert, P., and R. Assimiti, "RPL 2831 applicability in industrial networks", draft-ietf-roll- 2832 rpl-industrial-applicability-02 (work in progress), 2833 October 2013. 2835 [I-D.ietf-tictoc-1588overmpls] 2836 Davari, S., Oren, A., Bhatia, M., Roberts, P., and L. 2837 Montini, "Transporting Timing messages over MPLS 2838 Networks", draft-ietf-tictoc-1588overmpls-07 (work in 2839 progress), October 2015. 2841 [I-D.kh-spring-ip-ran-use-case] 2842 Khasnabish, B., hu, f., and L. Contreras, "Segment Routing 2843 in IP RAN use case", draft-kh-spring-ip-ran-use-case-02 2844 (work in progress), November 2014. 2846 [I-D.svshah-tsvwg-deterministic-forwarding] 2847 Shah, S. and P. Thubert, "Deterministic Forwarding PHB", 2848 draft-svshah-tsvwg-deterministic-forwarding-04 (work in 2849 progress), August 2015. 2851 [I-D.thubert-6lowpan-backbone-router] 2852 Thubert, P., "6LoWPAN Backbone Router", draft-thubert- 2853 6lowpan-backbone-router-03 (work in progress), February 2854 2013. 2856 [I-D.wang-6tisch-6top-sublayer] 2857 Wang, Q. and X. Vilajosana, "6TiSCH Operation Sublayer 2858 (6top)", draft-wang-6tisch-6top-sublayer-04 (work in 2859 progress), November 2015. 2861 [IEC61850-90-12] 2862 TC57 WG10, IEC., "IEC 61850-90-12 TR: Communication 2863 networks and systems for power utility automation - Part 2864 90-12: Wide area network engineering guidelines", 2015. 2866 [IEC62439-3:2012] 2867 TC65, IEC., "IEC 62439-3: Industrial communication 2868 networks - High availability automation networks - Part 3: 2869 Parallel Redundancy Protocol (PRP) and High-availability 2870 Seamless Redundancy (HSR)", 2012. 2872 [IEEE1588] 2873 IEEE, "IEEE Standard for a Precision Clock Synchronization 2874 Protocol for Networked Measurement and Control Systems", 2875 IEEE Std 1588-2008, 2008, 2876 . 2879 [IEEE1722] 2880 IEEE, "1722-2011 - IEEE Standard for Layer 2 Transport 2881 Protocol for Time Sensitive Applications in a Bridged 2882 Local Area Network", IEEE Std 1722-2011, 2011, 2883 . 2886 [IEEE19043] 2887 IEEE Standards Association, "IEEE 1904.3 TF", IEEE 1904.3, 2888 2015, . 2890 [IEEE802.1TSNTG] 2891 IEEE Standards Association, "IEEE 802.1 Time-Sensitive 2892 Networks Task Group", March 2013, 2893 . 2895 [IEEE802154] 2896 IEEE standard for Information Technology, "IEEE std. 2897 802.15.4, Part. 15.4: Wireless Medium Access Control (MAC) 2898 and Physical Layer (PHY) Specifications for Low-Rate 2899 Wireless Personal Area Networks". 2901 [IEEE802154e] 2902 IEEE standard for Information Technology, "IEEE standard 2903 for Information Technology, IEEE std. 802.15.4, Part. 2904 15.4: Wireless Medium Access Control (MAC) and Physical 2905 Layer (PHY) Specifications for Low-Rate Wireless Personal 2906 Area Networks, June 2011 as amended by IEEE std. 2907 802.15.4e, Part. 15.4: Low-Rate Wireless Personal Area 2908 Networks (LR-WPANs) Amendment 1: MAC sublayer", April 2909 2012. 2911 [IEEE8021AS] 2912 IEEE, "Timing and Synchronizations (IEEE 802.1AS-2011)", 2913 IEEE 802.1AS-2001, 2011, 2914 . 2917 [IEEE8021CM] 2918 Farkas, J., "Time-Sensitive Networking for Fronthaul", 2919 Unapproved PAR, PAR for a New IEEE Standard; 2920 IEEE P802.1CM, April 2015, 2921 . 2924 [IEEE8021TSN] 2925 IEEE 802.1, "The charter of the TG is to provide the 2926 specifications that will allow time-synchronized low 2927 latency streaming services through 802 networks.", 2016, 2928 . 2930 [IETFDetNet] 2931 IETF, "Charter for IETF DetNet Working Group", 2015, 2932 . 2934 [ISA100] ISA/ANSI, "ISA100, Wireless Systems for Automation", 2935 . 2937 [ISA100.11a] 2938 ISA/ANSI, "Wireless Systems for Industrial Automation: 2939 Process Control and Related Applications - ISA100.11a-2011 2940 - IEC 62734", 2011, . 2943 [ISO7240-16] 2944 ISO, "ISO 7240-16:2007 Fire detection and alarm systems -- 2945 Part 16: Sound system control and indicating equipment", 2946 2007, . 2949 [knx] KNX Association, "ISO/IEC 14543-3 - KNX", November 2006. 2951 [lontalk] ECHELON, "LonTalk(R) Protocol Specification Version 3.0", 2952 1994. 2954 [LTE-Latency] 2955 Johnston, S., "LTE Latency: How does it compare to other 2956 technologies", March 2014, 2957 . 2960 [MEF] MEF, "Mobile Backhaul Phase 2 Amendment 1 -- Small Cells", 2961 MEF 22.1.1, July 2014, 2962 . 2965 [METIS] METIS, "Scenarios, requirements and KPIs for 5G mobile and 2966 wireless system", ICT-317669-METIS/D1.1 ICT- 2967 317669-METIS/D1.1, April 2013, . 2970 [modbus] Modbus Organization, "MODBUS APPLICATION PROTOCOL 2971 SPECIFICATION V1.1b", December 2006. 2973 [net5G] Ericsson, "5G Radio Access, Challenges for 2020 and 2974 Beyond", Ericsson white paper wp-5g, June 2013, 2975 . 2977 [NGMN] NGMN Alliance, "5G White Paper", NGMN 5G White Paper v1.0, 2978 February 2015, . 2981 [NGMN-fronth] 2982 NGMN Alliance, "Fronthaul Requirements for C-RAN", March 2983 2015, . 2986 [PCE] IETF, "Path Computation Element", 2987 . 2989 [profibus] 2990 IEC, "IEC 61158 Type 3 - Profibus DP", January 2001. 2992 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 2993 Requirement Levels", BCP 14, RFC 2119, 2994 DOI 10.17487/RFC2119, March 1997, 2995 . 2997 [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 2998 (IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460, 2999 December 1998, . 3001 [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, 3002 "Definition of the Differentiated Services Field (DS 3003 Field) in the IPv4 and IPv6 Headers", RFC 2474, 3004 DOI 10.17487/RFC2474, December 1998, 3005 . 3007 [RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol 3008 Label Switching Architecture", RFC 3031, 3009 DOI 10.17487/RFC3031, January 2001, 3010 . 3012 [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., 3013 and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP 3014 Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001, 3015 . 3017 [RFC3393] Demichelis, C. and P. Chimento, "IP Packet Delay Variation 3018 Metric for IP Performance Metrics (IPPM)", RFC 3393, 3019 DOI 10.17487/RFC3393, November 2002, 3020 . 3022 [RFC3444] Pras, A. and J. Schoenwaelder, "On the Difference between 3023 Information Models and Data Models", RFC 3444, 3024 DOI 10.17487/RFC3444, January 2003, 3025 . 3027 [RFC3972] Aura, T., "Cryptographically Generated Addresses (CGA)", 3028 RFC 3972, DOI 10.17487/RFC3972, March 2005, 3029 . 3031 [RFC3985] Bryant, S., Ed. and P. Pate, Ed., "Pseudo Wire Emulation 3032 Edge-to-Edge (PWE3) Architecture", RFC 3985, 3033 DOI 10.17487/RFC3985, March 2005, 3034 . 3036 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing 3037 Architecture", RFC 4291, DOI 10.17487/RFC4291, February 3038 2006, . 3040 [RFC4553] Vainshtein, A., Ed. and YJ. Stein, Ed., "Structure- 3041 Agnostic Time Division Multiplexing (TDM) over Packet 3042 (SAToP)", RFC 4553, DOI 10.17487/RFC4553, June 2006, 3043 . 3045 [RFC4903] Thaler, D., "Multi-Link Subnet Issues", RFC 4903, 3046 DOI 10.17487/RFC4903, June 2007, 3047 . 3049 [RFC4919] Kushalnagar, N., Montenegro, G., and C. Schumacher, "IPv6 3050 over Low-Power Wireless Personal Area Networks (6LoWPANs): 3051 Overview, Assumptions, Problem Statement, and Goals", 3052 RFC 4919, DOI 10.17487/RFC4919, August 2007, 3053 . 3055 [RFC5086] Vainshtein, A., Ed., Sasson, I., Metz, E., Frost, T., and 3056 P. Pate, "Structure-Aware Time Division Multiplexed (TDM) 3057 Circuit Emulation Service over Packet Switched Network 3058 (CESoPSN)", RFC 5086, DOI 10.17487/RFC5086, December 2007, 3059 . 3061 [RFC5087] Stein, Y(J)., Shashoua, R., Insler, R., and M. Anavi, 3062 "Time Division Multiplexing over IP (TDMoIP)", RFC 5087, 3063 DOI 10.17487/RFC5087, December 2007, 3064 . 3066 [RFC6282] Hui, J., Ed. and P. Thubert, "Compression Format for IPv6 3067 Datagrams over IEEE 802.15.4-Based Networks", RFC 6282, 3068 DOI 10.17487/RFC6282, September 2011, 3069 . 3071 [RFC6550] Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J., 3072 Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur, 3073 JP., and R. Alexander, "RPL: IPv6 Routing Protocol for 3074 Low-Power and Lossy Networks", RFC 6550, 3075 DOI 10.17487/RFC6550, March 2012, 3076 . 3078 [RFC6551] Vasseur, JP., Ed., Kim, M., Ed., Pister, K., Dejean, N., 3079 and D. Barthel, "Routing Metrics Used for Path Calculation 3080 in Low-Power and Lossy Networks", RFC 6551, 3081 DOI 10.17487/RFC6551, March 2012, 3082 . 3084 [RFC6775] Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C. 3085 Bormann, "Neighbor Discovery Optimization for IPv6 over 3086 Low-Power Wireless Personal Area Networks (6LoWPANs)", 3087 RFC 6775, DOI 10.17487/RFC6775, November 2012, 3088 . 3090 [RFC7554] Watteyne, T., Ed., Palattella, M., and L. Grieco, "Using 3091 IEEE 802.15.4e Time-Slotted Channel Hopping (TSCH) in the 3092 Internet of Things (IoT): Problem Statement", RFC 7554, 3093 DOI 10.17487/RFC7554, May 2015, 3094 . 3096 [SRP_LATENCY] 3097 Gunther, C., "Specifying SRP Latency", 2014, 3098 . 3101 [STUDIO_IP] 3102 Mace, G., "IP Networked Studio Infrastructure for 3103 Synchronized & Real-Time Multimedia Transmissions", 2007, 3104 . 3107 [SyncE] ITU-T, "G.8261 : Timing and synchronization aspects in 3108 packet networks", Recommendation G.8261, August 2013, 3109 . 3111 [TEAS] IETF, "Traffic Engineering Architecture and Signaling", 3112 . 3114 [TS23401] 3GPP, "General Packet Radio Service (GPRS) enhancements 3115 for Evolved Universal Terrestrial Radio Access Network 3116 (E-UTRAN) access", 3GPP TS 23.401 10.10.0, March 2013. 3118 [TS25104] 3GPP, "Base Station (BS) radio transmission and reception 3119 (FDD)", 3GPP TS 25.104 3.14.0, March 2007. 3121 [TS36104] 3GPP, "Evolved Universal Terrestrial Radio Access 3122 (E-UTRA); Base Station (BS) radio transmission and 3123 reception", 3GPP TS 36.104 10.11.0, July 2013. 3125 [TS36133] 3GPP, "Evolved Universal Terrestrial Radio Access 3126 (E-UTRA); Requirements for support of radio resource 3127 management", 3GPP TS 36.133 12.7.0, April 2015. 3129 [TS36211] 3GPP, "Evolved Universal Terrestrial Radio Access 3130 (E-UTRA); Physical channels and modulation", 3GPP 3131 TS 36.211 10.7.0, March 2013. 3133 [TS36300] 3GPP, "Evolved Universal Terrestrial Radio Access (E-UTRA) 3134 and Evolved Universal Terrestrial Radio Access Network 3135 (E-UTRAN); Overall description; Stage 2", 3GPP TS 36.300 3136 10.11.0, September 2013. 3138 [TSNTG] IEEE Standards Association, "IEEE 802.1 Time-Sensitive 3139 Networks Task Group", 2013, 3140 . 3142 [UHD-video] 3143 Holub, P., "Ultra-High Definition Videos and Their 3144 Applications over the Network", The 7th International 3145 Symposium on VICTORIES Project PetrHolub_presentation, 3146 October 2014, . 3149 [WirelessHART] 3150 www.hartcomm.org, "Industrial Communication Networks - 3151 Wireless Communication Network and Communication Profiles 3152 - WirelessHART - IEC 62591", 2010. 3154 Authors' Addresses 3156 Ethan Grossman (editor) 3157 Dolby Laboratories, Inc. 3158 1275 Market Street 3159 San Francisco, CA 94103 3160 USA 3162 Phone: +1 415 645 4726 3163 Email: ethan.grossman@dolby.com 3164 URI: http://www.dolby.com 3166 Craig Gunther 3167 Harman International 3168 10653 South River Front Parkway 3169 South Jordan, UT 84095 3170 USA 3172 Phone: +1 801 568-7675 3173 Email: craig.gunther@harman.com 3174 URI: http://www.harman.com 3175 Pascal Thubert 3176 Cisco Systems, Inc 3177 Building D 3178 45 Allee des Ormes - BP1200 3179 MOUGINS - Sophia Antipolis 06254 3180 FRANCE 3182 Phone: +33 497 23 26 34 3183 Email: pthubert@cisco.com 3185 Patrick Wetterwald 3186 Cisco Systems 3187 45 Allees des Ormes 3188 Mougins 06250 3189 FRANCE 3191 Phone: +33 4 97 23 26 36 3192 Email: pwetterw@cisco.com 3194 Jean Raymond 3195 Hydro-Quebec 3196 1500 University 3197 Montreal H3A3S7 3198 Canada 3200 Phone: +1 514 840 3000 3201 Email: raymond.jean@hydro.qc.ca 3203 Jouni Korhonen 3204 Broadcom Corporation 3205 3151 Zanker Road 3206 San Jose, CA 95134 3207 USA 3209 Email: jouni.nospam@gmail.com 3211 Yu Kaneko 3212 Toshiba 3213 1 Komukai-Toshiba-cho, Saiwai-ku, Kasasaki-shi 3214 Kanagawa, Japan 3216 Email: yu1.kaneko@toshiba.co.jp 3217 Subir Das 3218 Applied Communication Sciences 3219 150 Mount Airy Road, Basking Ridge 3220 New Jersey, 07920, USA 3222 Email: sdas@appcomsci.com 3224 Yiyong Zha 3225 Huawei Technologies 3227 Email: zhayiyong@huawei.com 3229 Balazs Varga 3230 Ericsson 3231 Konyves Kalman krt. 11/B 3232 Budapest 1097 3233 Hungary 3235 Email: balazs.a.varga@ericsson.com 3237 Janos Farkas 3238 Ericsson 3239 Konyves Kalman krt. 11/B 3240 Budapest 1097 3241 Hungary 3243 Email: janos.farkas@ericsson.com 3245 Franz-Josef Goetz 3246 Siemens 3247 Gleiwitzerstr. 555 3248 Nurnberg 90475 3249 Germany 3251 Email: franz-josef.goetz@siemens.com 3253 Juergen Schmitt 3254 Siemens 3255 Gleiwitzerstr. 555 3256 Nurnberg 90475 3257 Germany 3259 Email: juergen.jues.schmitt@siemens.com